engine-manage-domains: Adding man page

Fix change I26e69ce141 engine-manage-domains.8

Change-Id: Icd979479d40c0cdae1db17bfbcffb0ecca5cd0b2
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=742421
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>