ip: punt socket - take the tags in Ethernet header into consideration

ip: punt socket - take the tags in Ethernet header into consideration

The punt socket code rewinds the current_data pointer by sizeof (ethernet_header_t),
which is incorrect if the header is tagged - resulting in truncated destination MAC
address. Use ethernet_buffer_header_size() instead, which takes tags into account.

Also add the unittest that verifies the issue and the fix.

Type: fix
Change-Id: I6352a174df144ca1e4230390c126f4b698724ebc
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>