Organize limits units and per-units constants

During v3 api review there was an agreement that would be nice to move limits
constants to utils file and refactor its usage inside limits api to avoid
unnecessary code duplication.

Also changed TestLimiter class to MockLimiter since that name can be confuse to
some unit test frameworks.

Change-Id: I1b8626e8d1e3257333d4dfee61591fd4cde82bd1
Baremetal_deploy_helper error message formatting.

Updates our baremetal_deploy_helper so our error message use
formatting that works with translations.

Change-Id: I8811df50f0e80c5680e6316c829a197b0ade5967
Fix metadata access in prep for instance objects

Related to blueprint unified-object-model
Fixes: bug #1192012

Change-Id: I8b708dc3d89fedfcb4bbf5d26b959da1298b0525
Merge "Organize limits units and per-units constants"
Merge "Baremetal_deploy_helper error message formatting."
Merge "Fix metadata access in prep for instance objects"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp