activate an already existing generic user

Change-Id: I85b000889d21f017c412116c33754bab5e7ef002
unset generic user is available through SOAP API

Change-Id: I20684d76b6b10f78985a61aaf3b39276b570e020
Merge remote-tracking branch 'gerrit/4049_delete_generic_user' into tuleap-stable-master

* gerrit/4049_delete_generic_user:
  unset generic user is available through SOAP API
  activate an already existing generic user

Change-Id: Ieb4d0fbe1e9632e2f9db27c27296f6ad9c80ab46
Tuleap 6.2.99.5

Change-Id: Id32ddd1bbc3094217be568beca710e9e1de42b24