tools: Removes inclusion of config file in engine-manage-domains.sh

Removes unneeded inclusion of engine-manage-domains.conf in
engine-manage-domains.sh. The variables contained in this file are
needed later in java code, but not in engine-manage-domains.sh.

Change-Id: Ia26468cbcc64c44adb9805c258f1625c574b4ab5
Bug-Url: https://bugzilla.redhat.com/904029
Signed-off-by: Martin Perina <mperina@redhat.com>