webadmin: Fixed capitalization on "New Cluster".

Fixed Capitalization on the "New Cluster" dialog.
The text:       "Migrate only Highly Available Virtual Machines"
was changed to: "Migrate Only Highly Available Virtual Machines"
in order to match the capitalization with the two other options.

Change-Id: I9ea28360b7554d45b26df9194fc420ab8249f31b
Bug-Url: https://bugzilla.redhat.com/1147987
Signed-off-by: Tomer Saban <tsaban@redhat.com>