The serve() and stop() functions should return accumulated errors

[codegold79]

@daved noted in PR #153,

This function (serve()) and stop() should be returning the accumulated errors as noted in the TODOs. Please create an issue for that if one does not exist.

His comment was in reference to the functions in the back/cmd/openbsrv/srvmgmt.go file.

He also noted in regard to the main.go file,

file an issue to sort out how we want errors to bubble back up to main.

For this issue, accumulate and return errors from the two functions in srvmgmt.go file, as well as stop() function called in main.go.