fix run_process action after retriggering (#215)

Author: Nikhil-Singhal-06

scenario_execution/scenario_execution/actions/run_process.py

@@ -44,6 +44,7 @@ def execute(self, command=None, wait_for_shutdown=True, shutdown_timeout=10, shu
         self.wait_for_shutdown = wait_for_shutdown
         self.shutdown_timeout = shutdown_timeout
         self.shutdown_signal = shutdown_signal[1]
+        self.executed = False
 
     def update(self) -> py_trees.common.Status:
         """