engine: Add separate validation for multicast MAC address

Split MAC address format validation into two separate ones:
1. Valid MAC address
2. Unicast MAC address

Change-Id: I4077a14fb61c2e082db9f81f1ded3b25ca98fc3f
Bug-Url: https://bugzilla.redhat.com/1118385
Signed-off-by: Yevgeny Zaspitsky <yzaspits@redhat.com>