fixes python3 TypeError; python2 intact
fixes python3 TypeError; python2 intact

exception in vpp_api.vac_write():
"TypeError: initializer for ctype 'char *' must be a bytes or list or
tuple, not str"

Change-Id: Ib6bcfb86e6e36c557174979a110113af689c6754
Signed-off-by: Andrey "Zed" Zaikin <647130d024d247e067b3097ad3b9d31c779b1c0f@gmail.com>

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