The util-linux's ptest uses the SCSI_DEBUG kernel module to create
virtual SCSI disks. The automount feature of udevd will try to mount
these disks by default. Because udevd controls the mount of the disks,
the eject/mount tests will fail or be skipped. This change will stop
udevd before executing the util-linux's ptest and start the daemon
again after all the tests.
This is for eudevd only, systemd-udevd doesn't present this problem
because there are no automount rules.
