Fix --produce_manifest flag in validate_failures.py.

Fix --produce_manifest flag in validate_failures.py.

When I added the functionality to use other summary files for
reporting, I broke the generation of manifests. When sum files are
passed on, we need to use the list. Otherwise, we need to find summary
files in the build directory.

This patch factors out that logic into a new function and calls it
from both the reporting and generation routines.

Committed to trunk.

	* testsuite-management/validate_failures.py (CollectSumFiles):
	Rename from GetSumFiles.
	(GetSumFiles): Factor out of CheckExpectedResults.
	(CheckExpectedResults): Call it.
	(ProduceManifest): Call it.

From-SVN: r189662