ping command does not work when there is woker thread (VPP-844)
ping command does not work when there is woker thread (VPP-844)

Change-Id: Ic896b237a7d141243e1b7d6d4fbb2a120f44363e
Signed-off-by: flyingeagle23 <4e6d007bdb0a091c64b73285859226e62f2cbe24@zte.com.cn>

vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,chrisy/vpp