webadmin: truncated text in VMs-Snapshots sub-tab

Fixed truncated headers in VMs -> Snapshots sub-tab.

Change-Id: I2e9586f77343645a74727452e58052c8b659e5fc
Bug-Url: https://bugzilla.redhat.com/951067
Bug-Url: https://bugzilla.redhat.com/950289
Signed-off-by: Daniel Erez <derez@redhat.com>