Have xfstest pass when using args

The xfstests's golden output includes the full set of tests we expect to
run when no args are specified.  If we specify args then the set of
tests can change and the test will always fail when they do.

This fixes that by having the test check the set of tests itself, rather
than relying on golden output.  If args are specified then our xfstest
only fails if any of the executed xfstest tests failed.  Without args,
we perform the same scraping of the check output and compare it against
the expected results ourself.

It would have been a bit much to put that large file inline in the test
file, so we add a dir of per-test files in revision control.  We can
also put the list of exclusions there.

We can also clean up the output redirection helper functions to make
them more clear.  After xfstests has executed we want to redirect output
back to the compared output so that we can catch any unexpected output.

Signed-off-by: Zach Brown <zab@versity.com>

tests/funcs/exec.sh

@@ -64,21 +64,27 @@ t_rc()
 }
 
 #
-# redirect test output back to the output of the invoking script intead
-# of the compared output.
+# As run, stdout/err are redirected to a file that will be compared with
+# the stored expected golden output of the test.  This redirects
+# stdout/err in the script to stdout of the invoking run-test.  It's
+# intended to give visible output of tests without being included in the
+# golden output.
 #
-t_restore_output()
+# (see the goofy "exec" fd manipulation in the main run-tests as it runs
+# each test)
+#
+t_stdout_invoked()
 {
 	exec >&6 2>&1
 }
 
 #
-# redirect a command's output back to the compared output after the
-# test has restored its output
+# This undoes t_stdout_invokved, returning the test's stdout/err to the
+# output file as it was when it was launched.
 #
-t_compare_output()
+t_stdout_compare()
 {
-	"$@" >&7 2>&1
+	exec >&7 2>&1
 }
 
 #