do not build metrics off compute.instance.create.start as it
doesn't have enough information in it to push to Gnocchi. there is
an .end event that happens seconds later so .start event has little
value outside context of event.
we change fnmatch to regex for more useful regex comparison and it's
faster
not a complete fix as compute.instance.update also is missing host
value occasionally
Partial-Bug: #1718290
Change-Id: I2aa7045873fd740255a3be5f64b9e9f5fd94e2d4
3a5fd619fa