don't write a pid file

This was likely used to avoid multiple instances but this is supported for
several years.

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/init.py

@@ -323,13 +323,6 @@ class OfflineImap:
 
         self.config is supposed to have been correctly initialized
         already."""
-        try:
-            pidfd = open(self.config.getmetadatadir() + "/pid", "w")
-            pidfd.write(str(os.getpid()) + "\n")
-            pidfd.close()
-        except:
-            pass
-
         try:
             # Honor CLI --account option, only.
             # Accounts to sync are put into syncaccounts variable.