SCTX-525: Reduce number of round-trips in the "PIF resynchronisation" logic
SCTX-525: Reduce number of round-trips in the "PIF resynchronisation" logic

Pool:
* 5 hosts
* 300 VLANs (none in use)
xapi start time decreased from 129s to 100s.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

koushikcgit/xcp-rrdd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,djs55/xcp-networkd,sharady/xcp-networkd,robhoes/squeezed,johnelse/xcp-rrdd,johnelse/xcp-rrdd,koushikcgit/xcp-rrdd,koushikcgit/xcp-networkd,koushikcgit/xcp-networkd,djs55/xcp-rrdd,simonjbeaumont/xcp-rrdd,djs55/squeezed,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,djs55/xcp-networkd