Sync install_venv_common from oslo

Change-Id: I1649a8e777baf288b3aa4c2c29e2fe532dfe93be
Implement ability to extend volume for v1.

Backport implementation from v2 to v1.

Change-Id: Ibb2334859e937a37481308580b072daef068f511
Fix wrong method call for extend subcommand

Ensure extend is called instead of extend_volume
as the latter doesn't exist.

Change-Id: I5a4ce5904dc73586a124f7bddebc8ffd30841980
Merge "Sync install_venv_common from oslo"
Merge "Implement ability to extend volume for v1."