Ensure Redish importer implements dependency management (go mod)

Modify the Redfish Importer to manage its dependencies using `go mod`. The voltha repositories (voltha-go, etc) may be useful as an example.

https://blog.golang.org/using-go-modules may be a useful tutorial.

make lint-sanity errors added lint-sanity and lint-mod 

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root@ip-10-5-1-11:~/cord/device-management# make lint-sanity

Running sanity check...

1. github.com/opencord/device-management/demo_test

demo_test/test.go:63:2: Println arg list ends with redundant newline

demo_test/test.go:81:2: Println arg list ends with redundant newline

demo_test/test.go:96:2: Println arg list ends with redundant newline

demo_test/test.go:111:2: Println arg list ends with redundant newline

demo_test/test.go:126:2: Println arg list ends with redundant newline

demo_test/test.go:144:2: Println arg list ends with redundant newline

demo_test/test.go:162:2: Println arg list ends with redundant newline

demo_test/test.go:176:2: Println arg list ends with redundant newline

demo_test/test.go:198:3: Error call has possible formatting directive %s

demo_test/test.go:208:5: Error call has possible formatting directive %s

demo_test/test.go:210:5: Info call has possible formatting directive %s

demo_test/test.go:254:3: Fatal call has possible formatting directive %v

demo_test/test.go:261:3: Fatal call has possible formatting directive %v

demo_test/test.go:267:4: Fatal call has possible formatting directive %v

demo_test/test.go:323:5: Print call has possible formatting directive %d

1. github.com/opencord/device-management

./main.go:78:2: Println arg list ends with redundant newline

./main.go:100:2: Println arg list ends with redundant newline

./main.go:113:2: Println arg list ends with redundant newline

./main.go:135:2: Println arg list ends with redundant newline

./main.go:167:2: Println arg list ends with redundant newline

./main.go:281:2: Println arg list ends with redundant newline

./main.go:307:3: Println call has possible formatting directive %v

./main.go:313:3: Println call has possible formatting directive %v

Makefile:100: recipe for target 'lint-sanity' failed

root@ip-10-5-1-11:~/cord/device-management# make lint-mod

Running dependency check...

all modules verified

Dependency check OK

make: *** [lint-sanity] Error 2