engine: Support detaching two labeled networks from a cluster

Instead of sending a sequential setup networks command when
multiple networks are being detached from a cluster on the same
host, a single setup networks request should be sent from the
engine to the host to avoid the failure of the latter.

Change-Id: I4a430d95b370a32ca38f7241e2816d3a5d476998
Bug-Url: https://bugzilla.redhat.com/1055188
Signed-off-by: Moti Asayag <masayag@redhat.com>