No test files for main.go and context.go

[rockyhwang]

$ make unit-test

Running pkg unit tests...
? github.com/trustbloc/sidetree-mock/cmd/sidetree-server [no test files]
? github.com/trustbloc/sidetree-mock/pkg/context [no test files]
ok github.com/trustbloc/sidetree-mock/pkg/httpserver 1.034s coverage: 94.4% of statements
ok github.com/trustbloc/sidetree-mock/pkg/observer 2.025s coverage: 100.0% of statements