fix(vlan): do not apply strip offload

fix(vlan): do not apply strip offload

Some tests (bonding) are failing as VPP refuses startup.conf.
That is because the config parameter support has been removed:
https://gerrit.fd.io/r/c/vpp/+/34822
That is VPP commit 8c8531c15c9195c2c82695eff6e70887de67fd88.

According to commit message, it was just a workaround
for Cisco ENIC cards, which are no longer tested in CSIT.

+ Delete 1 robot and 1 python keyword as they become unused.

Change-Id: If53e324a27cfbd4659e49ab8bcd03253642dde96
Signed-off-by: Vratko Polak <vrpolak@cisco.com>