Attach Manila shares via virtiofs (manila abstraction)

This patch is inspired by /nova/volume/cinder.py, it is an abstraction to
the manila service.

Manila is the OpenStack Shared Filesystems service.
These series of patches implement changes required in Nova to allow the shares
provided by Manila to be associated with and attached to instances using
virtiofs.

Implements: blueprint libvirt-virtiofs-attach-manila-shares
Depends-On: https://review.opendev.org/c/openstack/openstacksdk/+/889519

Change-Id: I44ab37ec2c15fcfc351c42216660bda39461b163

requirements.txt

@@ -62,5 +62,5 @@ retrying>=1.3.3 # Apache-2.0
 os-service-types>=1.7.0 # Apache-2.0
 python-dateutil>=2.7.0 # BSD
 futurist>=1.8.0 # Apache-2.0
-openstacksdk>=0.35.0 # Apache-2.0
+openstacksdk>=4.0.0 # Apache-2.0
 PyYAML>=5.1 # MIT