Add -p 1 to an example restore_command in order to limit WAL-E to only a single thread

With out tests, the multi-threaded WAL fetch didn't work reliably with S3, resulting in stuck WAL-E processes.

patroni/scripts/wale_restore.py

@@ -22,7 +22,7 @@
 
 # currently also requires that you configure the restore_command to use wal_e, example:
 #       recovery_conf:
-#               restore_command: envdir /etc/wal-e.d/env wal-e wal-fetch "%f" "%p"
+#               restore_command: envdir /etc/wal-e.d/env wal-e wal-fetch "%f" "%p" -p 1
 
 from collections import namedtuple
 import logging