mavsdk_tests: use custom rootfs, reset it

Instead of messing with existing params, use a separate rootfs for
tests, as suggested by @bkueng.

test/mavsdk_tests/mavsdk_test_runner.py

@@ -3,7 +3,6 @@
 import argparse
 import datetime
 import fnmatch
-import glob
 import json
 import math
 import os
@@ -326,8 +325,6 @@ class Tester:
     def run_test_case(self, test: Dict[str, Any],
                       case: str, log_dir: str) -> bool:
 
-        self.clear_params()
-
         self.start_runners(log_dir, test, case)
 
         logfile_path = self.determine_logfile_path(log_dir, 'combined')
@@ -369,15 +366,6 @@ class Tester:
                 print("  - {}".format(runner.get_log_filename()))
         return is_success
 
-    def clear_params(self) -> None:
-        param_files = glob.glob(
-            "build/px4_sitl_default/tmp/rootfs/eeprom/parameters_*",
-            recursive=False)
-        for param_file in param_files:
-            if self.verbose:
-                print("Deleting param file: {}".format(param_file))
-            os.unlink(param_file)
-
     def start_runners(self,
                       log_dir: str,
                       test: Dict[str, Any],