webadmin: Suggest bond name when creating new bond

Ever since the user has been able to create new bonds from the engine,
the default suggest bond name was "bond" to show all existing bond
names upon focus. Now a valid bond name is suggested instead.

Change-Id: I059a02cca35c91bdf4c44ffbdfa88326fe20ee2f
Bug-Url: https://bugzilla.redhat.com/988425
Signed-off-by: Lior Vernia <lvernia@redhat.com>