webadmin: ImportVmFromExportDomainModel#doInit DLS

Removed the unused local variable cluster which was causing a FindBugs
warning.

Change-Id: Iaf9dc95b3099c202cebdf955db6706990f4cf0bf
Bug-Url: https://bugzilla.redhat.com/1168532
Signed-off-by: Allon Mureinik <amureini@redhat.com>