tests: Gather only files which need to built

Previous code would rather provide a filter but never look
for newly "Added" files leading to failures in subsequent
build.

This patch fixes such issue by actually verifying pedantically
for only files which need to be tested.

Change-Id: Ia716acf82ee60f8ffe5e36257f1cc866c6062718
BUG: 904005
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/6016
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>