Remove duplicate code to add group members

Adding group members is implemented in the AddMembers REST endpoint
and there is no need for the CreateGroup REST endpoint to implement
the same functionality again. Refactor the code in AddMembers so that
it can be reused from CreateGroup.

Change-Id: I79bfb06ebdd2da225d9667c68fc716d84f611563
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
2 files changed