utils.execute: Add a debug-level log to record stdin
utils.execute: Add a debug-level log to record stdin

It's important to record stdin than it used to be because
the recent versions of ovs_lib passes flow strings to
ovs-ofctl command via stdin.

Change-Id: I3b3d5742076e05a3d4ebf5adc26356742b2928e4

MaximNevrov/neutron,mmnelemane/neutron,jumpojoy/neutron,mahak/neutron,alexandrucoman/vbox-neutron-agent,huntxu/neutron,NeCTAR-RC/neutron,takeshineshiro/neutron,noironetworks/neutron,adelina-t/neutron,dhanunjaya/neutron,dims/neutron,chitr/neutron,jerryz1982/neutron,JianyuWang/neutron,yanheven/neutron,yuewko/neutron,watonyweng/neutron,shahbazn/neutron,bigswitch/neutron,vivekanand1101/neutron,apporc/neutron,Stavitsky/neutron,MaximNevrov/neutron,bigswitch/neutron,JioCloud/neutron,miyakz1192/neutron,SamYaple/neutron,paninetworks/neutron,paninetworks/neutron,wolverineav/neutron,SmartInfrastructures/neutron,suneeth51/neutron,igor-toga/local-snat,openstack/neutron,yanheven/neutron,waltBB/neutron_read,dims/neutron,mmnelemane/neutron,pnavarro/neutron,mandeepdhami/neutron,alexandrucoman/vbox-neutron-agent,eonpatapon/neutron,dhanunjaya/neutron,NeCTAR-RC/neutron,wenhuizhang/neutron,suneeth51/neutron,cisco-openstack/neutron,Stavitsky/neutron,SamYaple/neutron,eayunstack/neutron,sasukeh/neutron,mahak/neutron,barnsnake351/neutron,sasukeh/neutron,javaos74/neutron,openstack/neutron,mattt416/neutron,jacknjzhou/neutron,chitr/neutron,vivekanand1101/neutron,huntxu/neutron,cisco-openstack/neutron,watonyweng/neutron,wolverineav/neutron,mandeepdhami/neutron,eayunstack/neutron,swdream/neutron,infobloxopen/neutron,JianyuWang/neutron,barnsnake351/neutron,glove747/liberty-neutron,javaos74/neutron,miyakz1192/neutron,magic0704/neutron,aristanetworks/neutron,antonioUnina/neutron,mahak/neutron,magic0704/neutron,takeshineshiro/neutron,bgxavier/neutron,asgard-lab/neutron,klmitch/neutron,bgxavier/neutron,openstack/neutron,skyddv/neutron,swdream/neutron,aristanetworks/neutron,sebrandon1/neutron,cloudbase/neutron,jumpojoy/neutron,mattt416/neutron,apporc/neutron,cloudbase/neutron,JioCloud/neutron,asgard-lab/neutron,infobloxopen/neutron,silenci/neutron,antonioUnina/neutron,yuewko/neutron,skyddv/neutron,jacknjzhou/neutron,neoareslinux/neutron,klmitch/neutron,shahbazn/neutron,pnavarro/neutron,eonpatapon/neutron,glove747/liberty-neutron,neoareslinux/neutron,wenhuizhang/neutron,waltBB/neutron_read,jerryz1982/neutron,noironetworks/neutron,sebrandon1/neutron,SmartInfrastructures/neutron,igor-toga/local-snat,adelina-t/neutron,silenci/neutron