btrfs-progs: tests: common: add helper run_check_stdout

Sometimes we need to process the output of the command, but run_check
captures all the output into results file.

Signed-off-by: David Sterba <dsterba@suse.cz>

tests/common

@@ -21,6 +21,14 @@ run_check()
 	"$@" >> $RESULTS 2>&1 || _fail "failed: $@"
 }
 
+# same as run_check but the stderr+stdout output is duplicated on stdout and
+# can be processed further
+run_check_stdout()
+{
+	echo "############### $@" >> $RESULTS 2>&1
+	"$@" 2>&1 | tee -a $RESULTS || _fail "failed: $@"
+}
+
 check_prereq()
 {
 	if ! [ -f $TOP/$1 ]; then