ansible.cfg: Set remote_tmp

Many hosts (should) have `/tmp` mounted with the `noexec` flag, which
prevents Ansible modules written there from running. To work around
this, the `remote_tmp` configuration option should be set to a path
under `/var/tmp`, which is not mounted noexec.

ansible.cfg

@@ -8,3 +8,5 @@ fact_caching = jsonfile
 fact_caching_connection = .fact-cache
 
 vault_password_file = .vault-secret.sh
+
+remote_tmp = /var/tmp/.ansible-${USER}