[bfn]: Fix sigterm processing (#12952)

Why I did it
SIGTERM takes more than 10 seconds to be processed, so psud is stopped by SIGKILL, this causes unexpected behavior since data base is not cleared

How I did it
Decorate get_presence api to cancel it on SIGTERM signal in order to avoid long processing.

How to verify it
test_pmon_psud_stop_and_start_status
test_pmon_psud_term_and_start_status

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/psu.py

@@ -135,12 +135,16 @@ class Psu(PsuBase):
         :param self.index: An integer, 1-based self.index of the PSU of which to query status
         :return: Boolean, True if PSU is plugged, False if not
         """
+        @cancel_on_sigterm
         def psu_present_get(client):
             return client.pltfm_mgr.pltfm_mgr_pwr_supply_present_get(self.__index)
 
         status = False
         try:
-            status = thrift_try(psu_present_get)
+            status = thrift_try(psu_present_get, attempts=1)
+        except Exception as e:
+            if "Canceling" in str(e):
+                syslog.syslog(syslog.LOG_INFO, "{}".format(e))
         finally:
             return status