webadmin: style fixes in manage events popup.

Change-Id: Ie7b8063d60666bdbcaaeaa7347ff36b7a3ddc369
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1133572
Signed-off-by: Mooli Tayer <mtayer@redhat.com>
(cherry picked from commit fc8ccf4ca617cc876eb8df428ee25a7a9a765557)