More minor tweaks to speed up xmpp updates
More minor tweaks to speed up xmpp updates

o Do not use integerToString to encode afi and safi
o Use fill and copy instead of string::replace because the latter
  seems to allocate a new string internally to allow the possibility
  of overlap between input and output strings

Change-Id: I4c90eff9f12588441a9c0610e21823723849d27d
Partial-Bug: 1607132

nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller