webadmin: Cluster dialog overlapping checkboxes fixed

'Enable Virt Service' checkbox and 'Enable Gluster Service' checkbox
in New/Edit Cluster dialog  were overlapped in webkit based browsers
due to css browser specific media queries.

Change-Id: I07b3d83a0d2af26c6c722542bea7cdf402f7dd2e
Bug-Url: https://bugzilla.redhat.com/1138556
Signed-off-by: Jakub Niedermertl <jniederm@redhat.com>