Adds exact match filters to nova scheduler

Add exact match ram, disk, core filters which will match exact values
of requested metrics, this is required for Baremetal/Ironic instance
filtering.

Unit tests have been proposed to nova at
https://review.openstack.org/#/c/83728

Change-Id: I20faa1c17f4121429bbbea80e59b168095909b48
Closes-Bug: #1291396
Merge "Adds exact match filters to nova scheduler"