Remove remote_tmp setting

This is incompatible with having the jobdir root be anything other
than /tmp, as it is unlikely to exist on the remote host.

This was originally added in commit
176431ec1488fbde93c953972f639b8a31d173c8 but all the reasons we needed
it are no longer relevant.

Change-Id: Ib3edf0abb0db33143b92e6947f08e22a39ff0c77
diff --git a/zuul/executor/server.py b/zuul/executor/server.py
index 45937ef..6ee97b5 100644
--- a/zuul/executor/server.py
+++ b/zuul/executor/server.py
@@ -1415,8 +1415,6 @@
             config.write('hostfile = %s\n' % self.jobdir.inventory)
             config.write('local_tmp = %s/local_tmp\n' %
                          self.jobdir.ansible_cache_root)
-            config.write('remote_tmp = %s/remote_tmp\n' %
-                         self.jobdir.ansible_cache_root)
             config.write('retry_files_enabled = False\n')
             config.write('gathering = smart\n')
             config.write('fact_caching = jsonfile\n')