Remove exec from platform_reboot call to prevent reboot hang (sonic-n…

…et#1881)

Port fix from master to stop pmon service for reboot and soft-reboot

What I did
Remove exec from the platform_reboot call to handle any hang issue during reboot
Port missing fix from master : stop pmon service for reboot and soft-reboot

How I did it
Remove "exec" from " exec ${DEVPATH}/${PLATFORM}/${PLAT_REBOOT} $@"

How to verify it
Perform sudo reboot after DE initializing the platfom driver and see if the device gracefully reboots by /sbin/reboot after failing on platform_reboot.

scripts/reboot

@@ -22,13 +22,25 @@ function debug()
     logger "$@"
 }
 
+function stop_pmon_service()
+{
+     CONTAINER_STOP_RC=0
+     debug "Stopping pmon docker"
+     docker kill pmon &> /dev/null || CONTAINER_STOP_RC=$?
+     systemctl stop pmon || debug "Ignore stopping pmon error $?"
+     if [[ CONTAINER_STOP_RC -ne 0 ]]; then
+        debug "Failed killing container pmon RC $CONTAINER_STOP_RC ."
+     fi
+}
+
 function stop_sonic_services()
 {
     if [[ x"$ASIC_TYPE" != x"mellanox" ]]; then
         debug "Stopping syncd process..."
         docker exec -i syncd /usr/bin/syncd_request_shutdown --cold > /dev/null
         sleep 3
     fi
+    stop_pmon_service
 }
 
 function clear_warm_boot()
@@ -141,7 +153,7 @@ fi
 
 if [ -x ${DEVPATH}/${PLATFORM}/${PLAT_REBOOT} ]; then
     VERBOSE=yes debug "Rebooting with platform ${PLATFORM} specific tool ..."
-    exec ${DEVPATH}/${PLATFORM}/${PLAT_REBOOT} $@
+    ${DEVPATH}/${PLATFORM}/${PLAT_REBOOT} $@
 
     # There are a couple reasons execution reaches here:
     #

scripts/soft-reboot

@@ -27,13 +27,25 @@ function debug()
     logger "$@"
 }
 
+function stop_pmon_service()
+{
+     CONTAINER_STOP_RC=0
+     debug "Stopping pmon docker"
+     docker kill pmon &> /dev/null || CONTAINER_STOP_RC=$?
+     systemctl stop pmon || debug "Ignore stopping pmon error $?"
+     if [[ CONTAINER_STOP_RC -ne 0 ]]; then
+        debug "Failed killing container pmon RC $CONTAINER_STOP_RC ."
+     fi
+}
+
 function stop_sonic_services()
 {
     if [[ x"$ASIC_TYPE" != x"mellanox" ]]; then
         debug "Stopping syncd process..."
         docker exec -i syncd /usr/bin/syncd_request_shutdown --cold > /dev/null
         sleep 3
     fi
+    stop_pmon_service
 }
 
 function clear_lingering_reboot_config()