Fix Share Migration improper behavior for drivers

Tempest tests were not appropriate for driver-assisted migration,
so this was fixed.

Also, improved docstrings and fixed workflow for drivers when
implementing 2-phase migration to be accurate with tempest and
handle AZs, which were previously locked to the source share's
AZ.

Driver-assisted migration now creates an additional
share instance to better handle and support driver methods.

Updated allow_access and deny_access APIs to allow users to mount
migrating shares before issuing 'migration-complete'.

APIImpact

Closes-bug: #1594922
Change-Id: If4bfaf7e9d963b83c13a6fea241c2eda14f7f409
7 files changed
tree: 0da6c73382ce237de0b41be7e1971c6b4cefef83
  1. manila_tempest_tests/