engine: Improve import vm message when profile not found

If a vnic profile cannot be found while importing a vm to
the system, the message should include that warning.

In addition, the network name should be printed only once.

Change-Id: I2099756b3ff9c07a6c121a3601b8c7d1d5811e38
Bug-Url: https://bugzilla.redhat.com/1004386
Signed-off-by: Moti Asayag <masayag@redhat.com>