Revert "Avoid unnecessary automounting in KDiskFreeSpaceInfo::freeSpaceInfo"

This reverts commit 6246e99b.

It breaks KIO on CIFS mounts as the check for automounts copied over
from frameworks/kfileitem.cpp isDirectoryMounted() apparently matches
CIFS as well (and for some weird reason KIO checks for available space
before trying to copy files).

We'll probably have to return to v1 of the abovementioned commit, i.e.
checking for "autofs" explicitly. However, more testing is apparently
necessary to avoid further nasty surprises.

REVIEW: 117044
BUG: 334776
FIXED-IN: 4.13.2