manager runs on Mac, and other openpilot for PC fixes (#1037)

* use the openpilot/persist directory on PC

* manager runs on mac

* sim runs w/o carla

* fix params location in test

* that rmtree can fail and it's okay

* refactor params clear functionality

* set PARAMS_PATH

common/params.py

@@ -29,7 +29,7 @@ import fcntl
 import tempfile
 import threading
 from enum import Enum
-
+from common.basedir import PARAMS
 
 def mkdirs_exists_ok(path):
   try:
@@ -320,7 +320,7 @@ def write_db(params_path, key, value):
     lock.release()
 
 class Params():
-  def __init__(self, db='/data/params'):
+  def __init__(self, db=PARAMS):
     self.db = db
 
     # create the database if it doesn't exist...
@@ -328,6 +328,11 @@ class Params():
       with self.transaction(write=True):
         pass
 
+  def clear_all(self):
+    shutil.rmtree(self.db, ignore_errors=True)
+    with self.transaction(write=True):
+      pass
+
   def transaction(self, write=False):
     if write:
       return DBWriter(self.db)