Fix Linux- and FreeBSD-specific includes in test-related files.
Change calls to ETH_P_8021Q constant which is not defined in FreeBSD
to the ETHERTYPE_VLAN constant, which is common for Linux and FreeBSD.

Change-Id: Ia5a155ec835451d1033ca38c14fdfb9d4f1df5fd
Merge "Fix Linux- and FreeBSD-specific includes in test-related files. Change calls to ETH_P_8021Q constant which is not defined in FreeBSD to the ETHERTYPE_VLAN constant, which is common for Linux and FreeBSD."