pvscan: match device arg to filter symlink

pvscan: match device arg to filter symlink

This fixes an issue related to the optimization in
  "pvscan: only add device args to dev cache"

If the devices file is not used, and the lvm.conf filter
accepts devices via symlink names, then those devices won't
be accepted by pvscan for autoactivation.  To resolve this,
recognize when the filter contains symlinks and disable the
optimization.  When the optimization is disabled, a full
dev_cache_scan is performed, and symlinks are associated
with the device names passed to pvscan.  filter-regex
will accept a device if symlinks to that device are accepted.