This addresses comments from code review to add handling of PCPU during
the migration/copy of limits from the Nova database to Keystone. In
legacy quotas, there is no settable quota limit for PCPU, so the limit
for VCPU is used for PCPU. With unified limits, PCPU will have its own
quota limit, so for the automated migration command, we will simply
create a dedicated limit for PCPU that is the same value as the limit
for VCPU.
On the docs side, this adds more detail about the token authorization
settings needed to use the nova-manage limits migrate_to_unified_limits
CLI command and documents more OSC limit commands like show and delete.
Related to blueprint unified-limits-nova-tool-and-docs
Change-Id: Ifdb1691d7b25d28216d26479418ea323476fee1a
d42fe462be