param: grab the shutdown lock while writing params to the file

src/modules/systemlib/flashparams/flashparams.c

@@ -44,6 +44,7 @@
 
 #include <px4_defines.h>
 #include <px4_posix.h>
+#include <px4_shutdown.h>
 #include <string.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -158,6 +159,12 @@ out:
 
 		size_t buf_size = bson_encoder_buf_size(&encoder);
 
+		int shutdown_lock_ret = px4_shutdown_lock();
+
+		if (shutdown_lock_ret) {
+			PX4_ERR("px4_shutdown_lock() failed (%i)", shutdown_lock_ret);
+		}
+
 		/* Get a buffer from the flash driver with enough space */
 
 		uint8_t *buffer;
@@ -186,6 +193,11 @@ out:
 			free(enc_buff);
 			parameter_flashfs_free();
 		}
+
+		if (shutdown_lock_ret == 0) {
+			px4_shutdown_unlock();
+		}
+
 	}
 
 	return result;