Remove baremetal-compute-pxe.filters

The baremetal PXE driver doesn't seem to run dnsmasq at all, so remove
the rootwrap filter which allows it to do so. This was introduced by
commit a2f260f.

Change-Id: I4cc1127222b73af218a6a8808d0ad54478878af1
fix service_ref undefined problem.

Change-Id: I361c240a314a8f5ab41d4047780f7d385e360019
Fixes: bug #1102346
Merge "fix service_ref undefined problem."
Merge "Remove baremetal-compute-pxe.filters"