test: exit with code 1 when no fn tests are found

Prevents the test_runner from exiting silently with code 0 when no tests were found.

test/functional/test_runner.py

@@ -473,7 +473,7 @@ def main():
     if not enable_bitcoind:
         print("No functional tests to run.")
         print("Rerun ./configure with --with-daemon and then make")
-        sys.exit(0)
+        sys.exit(1)
 
     # Build list of tests
     test_list = []
@@ -522,7 +522,7 @@ def main():
     if not test_list:
         print("No valid test scripts specified. Check that your test is in one "
               "of the test lists in test_runner.py, or run test_runner.py with no arguments to run all tests")
-        sys.exit(0)
+        sys.exit(1)
 
     if args.help:
         # Print help for test_runner.py, then print help of the first script (with args removed) and exit.