Address dockerfile lint warnings

Not all of these are real issues, but all should be verified/checked.

Dockerfile.afrouter:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.afrouter:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouter:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouter:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouter:53 DL3003 Use WORKDIR to switch to a directory
Dockerfile.afrouter:53 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.afrouterTest:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.afrouterTest:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterTest:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterTest:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterTest:58 DL3003 Use WORKDIR to switch to a directory
Dockerfile.afrouterTest:58 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.afrouterTest:68 SC2019 Use '[:upper:]' to support accents and foreign alphabets.
Dockerfile.afrouterTest:68 SC2018 Use '[:lower:]' to support accents and foreign alphabets.
Dockerfile.afrouterTest:68 DL3003 Use WORKDIR to switch to a directory
Dockerfile.afrouterTest:68 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.afrouterTest:79 DL3003 Use WORKDIR to switch to a directory
Dockerfile.afrouterTest:97 DL3025 Use arguments JSON notation for CMD and ENTRYPOINT arguments
Dockerfile.afrouterd:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.afrouterd:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterd:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterd:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.afrouterd:53 DL3003 Use WORKDIR to switch to a directory
Dockerfile.afrouterd:53 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.ro_core:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.ro_core:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.ro_core:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.ro_core:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.ro_core:48 DL3003 Use WORKDIR to switch to a directory
Dockerfile.ro_core:48 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.rw_core:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.rw_core:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.rw_core:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.rw_core:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.rw_core:48 DL3003 Use WORKDIR to switch to a directory
Dockerfile.rw_core:48 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.simulated_olt:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.simulated_olt:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_olt:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_olt:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_olt:50 DL3003 Use WORKDIR to switch to a directory
Dockerfile.simulated_olt:50 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it
Dockerfile.simulated_onu:28 DL3018 Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
Dockerfile.simulated_onu:32 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_onu:33 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_onu:34 SC2086 Double quote to prevent globbing and word splitting.
Dockerfile.simulated_onu:50 DL3003 Use WORKDIR to switch to a directory
Dockerfile.simulated_onu:50 DL4006 Set the SHELL option -o pipefail before RUN with a pipe in it