webadmin: Increased width of provider popup

The Japanese translation for "Interface Mappings" would overlap with
the info icon before this change.

Change-Id: Ib35f8cfcf802c90ff1724fbfa1e8c4a523b704f5
Bug-Url: https://bugzilla.redhat.com/1000883
Signed-off-by: Lior Vernia <lvernia@redhat.com>