Resolves: #658344 - system-config-lvm leaves mount for LV in fstab after it was completely removed

In new distributions there was change in organization of devices in /dev/ and now 
there is not a symlink from /dev/vg/lv to /dev/mapper/vg-lv. This patch fixes this issue.

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#	modified:   Fstab.py
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#	../attachment.cgi?id=513606&action=diff&context=patch&collapsed=&headers=1&format=raw
#	cylinder_items.py~
