[contrib] validate_failures.py: Fix output of manifests

If we have the same .exp line in the two different "tools",
then we may skip the output of the .exp line if the entries
of two "tools" are processed back-to-back.  A missing .exp
line after a "tool" header will make for a corrupted manifest
file, which we will fail to accept as input later.

Change-Id: I965a917228ed2cb54ca14343e210e5ae5989500f
1 file changed