Fix greentea logic to be same as original

Author: Olli-Pekka Puolitaival

mbed/mbed.py

@@ -2740,13 +2740,19 @@ def test_(toolchain=None, target=None, compile_list=False, run_list=False, compi
 
         # Greentea tests
         if greentea:
-            greentea_command = ['mbedgt', '--test-spec', test_spec] \
-                      + (['-n', tests_by_name] if tests_by_name else []) \
-                      + (['-V'] if verbose else []) \
-                      + args
+            if run_list:
+                popen(['mbedgt', '--test-spec', test_spec, '--list']
+                      + (['-n', tests_by_name] if tests_by_name else [])
+                      + (['-V'] if verbose else [])
+                      + args,
+                      env=env)
 
             if run_only or build_and_run_tests:
-                popen(greentea_command, env=env)
+                popen(['mbedgt', '--test-spec', test_spec]
+                      + (['-n', tests_by_name] if tests_by_name else [])
+                      + (['-V'] if verbose else [])
+                      + args,
+                      env=env)
 
         # Icetea tests
         if icetea: