Ironic: don't canonicalize extra_specs data

Don't canonicalize the cpu_arch extra_specs field. This is important
because the scheduler filters which use extra specs don't canonicalize
things either and as such you'll have mismatched fields causing
instances not to get scheduled.

This was recently changed as part of the Ironic -> Nova driver patch
series. We still want to canonicalize supported_instances though...

Change-Id: I9342213b5433113816142b1f737119065e9f077f
Closes-bug: #1366859
Merge "Ironic: don't canonicalize extra_specs data"