engine: Improve setup networks failure message

Adding a message for a failed setup networks command
which was invoked with 'check connectivity'.

Change-Id: Id25f864970df7e7f420f760fa8e8c78c1104d64e
Bug-Url: https://bugzilla.redhat.com/1072794
Signed-off-by: Moti Asayag <masayag@redhat.com>