webadmin: Set Migrate On Error in Data Center Guide Me

The Add Cluster dialog in the Data Center "Guide Me" was not setting
the chosen Migrate On Error action in the VDSGroup instance that is
sent to the AddVdsGroup command.

Change-Id: I7498ae26f1ff2fcd90e547aae48fb66e25bb4a43
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1142658
Signed-off-by: Vitor de Lima <vdelima@redhat.com>