Accept unit test command as an input in the CLI during 'app create'
Accept unit test command as an input in the CLI during 'app create'

Accept the unit test command, as a '--unittest-cmd' flag during
'app create'

Today, the only way we can use the unittest feature is by providing
the test command in the planfile.

User should be able to pass in a test command on the command line.

Change-Id: I5d14adf51f8155f355fafbcfe74054c48188a22a
Closes-bug: 1444613

stackforge/python-solumclient,stackforge/python-solumclient,openstack/python-solumclient