tests: regression, can't run `prove $t` in subdirs

In various tests we already use the pattern:

  . $(dirname $0)/../include.rc

to locate various .rc files.

Use the same pattern we already use to also find the new env.rc

Change-Id: Ib7878c3f7f6491fcec401e9adbaa696ace392fae
BUG: 1142420
Signed-off-by: Kaleb S. KEITHLEY <kkeithle@redhat.com>
Reviewed-on: http://review.gluster.org/8753
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Tested-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>