[tooling] Make start_port_server less spammy when starting for the first time (#37628)

This has freaked more than one new team member out historically

Closes #37628

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/37628 from ctiller:cgf ded4d14b12
PiperOrigin-RevId: 677866795

tools/run_tests/python_utils/start_port_server.py

@@ -31,7 +31,7 @@ import jobset
 _PORT_SERVER_PORT = 32766
 
 
-def start_port_server():
+def start_port_server(verbose=False):
     # check if a compatible port server is running
     # if incompatible (version mismatch) ==> start a new one
     # if not running ==> start a new one
@@ -45,6 +45,7 @@ def start_port_server():
         logging.info("detected port server running version %d", version)
         running = True
     except Exception as e:
+        if verbose:
             logging.exception("failed to detect port server")
         running = False
     if running: