tools: managed-domains: Fix typo occured->occurred

Fix typo in the usage message and man page.

Change-Id: Id4f699e91730844ea09a99c943d9a3f52a68f91f
Bug-Url: https://bugzilla.redhat.com/1057176
Signed-off-by: Allon Mureinik <amureini@redhat.com>