Handle VLAN interfaces with Linux IP wrapper

Check if the interface name contains '@' character and use the part
before that character as interface name.

(cherry picked from commit 202fe60b646429aabeb2ef8b1430a1ba9b356061)
Closes-Bug: #1240125

Change-Id: I981c11ed0d62088a0774c09fbeef795f9987cc2f
Merge "Handle VLAN interfaces with Linux IP wrapper" into stable/havana