Fixes bug 1056246.
Reverts commit 0a09bf5faeb30b675fdb8f517c61166ef794bad3.
This ensures that we fail-fast if the tgtd configuration does
not include the directory for volume iscsi target configs,
instead of only blowing up when tgtd is restarted.
Change-Id: I3c9f0d97e411560e5c0fd058671f8c834e9bed1e