The dot1q_vlans & dot1ad_vlans should be reset to 0 when main interface
is deleted. Otherwise, VPP will crash if the same interface index is reused
without attaching the sub interface on it.
Change-Id: I484d4a8892ff4241a3a32b22189746193d5f2594 Signed-off-by: Steve Shin <jonshin@cisco.com>