(FACT-659) Fix Linux partition fact's filesystem regex.

The regex for extracting the filesystem from blkid does not properly
handle quoted values.  Currently it is matching all characters between
two double quotes, including a double quote character.

The fix is to match all characters except for a double quote between two
double quotes.  This prevents us from greedily matching more than the intended
value.
Merge pull request #765 from peterhuene/fact/659

(FACT-659) Fix Linux partition fact's filesystem regex.