Fix in fuelclient help message

 Moved --env flag back to subparsers
 thus resoving bug. Also removed some
 redundancy by adding required flags to
 actions data structure.

 Implements: blueprint cli-fix-doc-optional-and-required-arguments

Change-Id: I16d1486e46f23237ace991ea12bd211cf0aa7dd9
Merge "Fix in fuelclient help message"