Extend multipathed device should not require a reconfigure

[Gorka Eguileor]

When extending a multipathed SCSI volume os-brick calls `multipath_reconfigure` and that seems unnecessary, since there is no need to reconfigure ALL multipaths.

It should be enough to call the `multipathd resize map`.

In the best scenario calling reconfigure would delay the `resize map`, and in the worst case I believe it could even make the resize fail after some retries.

In my testing during the review of [1] I could remove the reconfigure on a system with 104 volumes and 417 paths and resizing worked just fine, though more testing is probably necessary.

[1]: https://review.opendev.org/c/openstack/os-brick/+/762776/7/os_brick/initiator/linuxscsi.py#657