Avoid OSError in get_blkdev_major_minor with network filesystems

To avoid OSError (File not found) thrown for volumes on network filesystems
during volume copy with CONF.volume_copy_bps_limit, this patch adds a check
of whether the specified file is on the local block devices to
get_blkdev_major_minor().

It also adds a testcase for get_blkdev_major_minor with a file on nfs and
fixes it with a regular file.

Change-Id: I0b725bba07ad632bfa0c922bfce1652efe59b033
Closes-Bug: 1348230
Merge "Avoid OSError in get_blkdev_major_minor with network filesystems"