terminal: improve condition on whether to display testpaths in header

Make it match better the condition on whether testpaths is used (found
in config/__init__.py).

src/_pytest/terminal.py

@@ -719,7 +719,7 @@ class TerminalReporter:
             line += ", configfile: " + bestrelpath(config.rootpath, config.inipath)
 
         testpaths = config.getini("testpaths")  # type: List[str]
-        if testpaths and config.args == testpaths:
+        if config.invocation_params.dir == config.rootpath and config.args == testpaths:
             line += ", testpaths: {}".format(", ".join(testpaths))
 
         result = [line]