Succeed if make check does not report any errors

Succeed if make check does not report any errors

The conditional that evaluates if there are any FAILed test cases
currently always fails, since we ensure it fails if we find any
unexpected results in tests.sum and it would obviously fail if it does
not find failed results in tests.sum.  This patch fixes this by simply
inverting the result of the egrep, i.e. succeed if egrep fails (to
find failed results) and fail if it succeeds.

Tested with 'make subdirs=localedata check' and 'make subdirs=locale
check' where all tests succeed and with 'make subdirs=elf check' where
a couple of tests fail for me.

	 * Makefile (summarize-tests): Fix return value on success.