fix: fix flaky pfc_storm (#15544)

Description of PR
Summary: Fix flaky pfc_storm stom_restored
Fixes # (issue) 30115860

Approach
What is the motivation for this PR?
Currently we detect flaky in detecting storm restore. The reason was because the storm terminated early and restore itself before LogAnalyzer can detect restoration.

As a result, we want to keep this to be stormed long enough.

After the end of each test case, we have stop_storm so it would be fine.

Signed-off-by: Austin Pham <austinpham@microsoft.com>

tests/pfcwd/test_pfcwd_function.py

@@ -463,7 +463,9 @@ def storm_setup(self, init=False, detect=True):
 
             if self.dut.topo_type == 't2' and self.fanout[self.peer_device].os == 'sonic':
                 gen_file = 'pfc_gen_t2.py'
-                pfc_send_time = 60
+                # We want to set the timer to be high here to keep the storm long enough for manual termination
+                # in the test instead of having it terminated by itself
+                pfc_send_time = 240
             else:
                 gen_file = 'pfc_gen.py'
                 pfc_send_time = None