Commit b20d39a5 introduced a new argument for the
virNetDevTapCreateInBridgePort function, however, its mock
in bhyve tests wasn't updated, so the build failed.

Fix build by adding this new argument to the mock version.

At this point unittest covers 4 basic cases:

 - minimal working XML for bhyve
 - same as above, but with virtio disk
 - ACPI and APIC args test
 - MAC address test