Previously linuxscsi.extend_volume would always attempt to wait for
multipath devices to appear regardless of multipath actually being used
by the connector.
This change corrects this by passing down the existing use_multipath
attribute from the iSCSI and FC connectors into linuxscsi.extend_volume.
The same attribute is introduced to the NVMe connector to also allow it
to skip this search for multipath devices.
Change-Id: I29d65ae036957f3a63cba93dd330b14e3361a1b9
Closes-bug: #1832247
9cf135c686