VPP-1649: fix coverity warning in api_format.c
VPP-1649: fix coverity warning in api_format.c

Change-Id: Idc22377ca705a45300faaf8acbc3cae5f10e1c92
Signed-off-by: Dave Barach <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@barachs.net>

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