Change default output-dir to be $HOME

In https://review.openstack.org/#/c/542875 we created --output-dir with
the default to $HOME/.undercloud-heat-installer which is not backward
compatible when you upgrade from a non-containerized undercloud.

Indeed, it'll fail to re-use the same passwords as the previous
deployment because the undercloud-passwords.conf file is in $HOME.

For backward compatibility, we should keep $HOME as default output_dir,
and allow deployers to override it.

Change-Id: I3b8464a3a2761d6cef319f2a1d08baedc9d8cc3e

releasenotes/notes/undercloud-deploy-tht-4af4b91774600e8f.yaml

@@ -14,8 +14,6 @@ features:
     configure ``undercloud install --use-heat`` behavior.
 upgrade:
   - |
-    The default value for `--output-dir` is changed for
-    undercloud heat installer to `$HOME/.undercloud-heat-installer`.
     The content of the processed heat templates will be persisted
     under the given path as `$output_dir/$tempdir/templates`, for
     each run of the undercloud deploy or install commands, unless

tripleoclient/constants.py

@@ -19,8 +19,7 @@ TRIPLEO_HEAT_TEMPLATES = "/usr/share/openstack-tripleo-heat-templates/"
 OVERCLOUD_YAML_NAME = "overcloud.yaml"
 OVERCLOUD_ROLES_FILE = "roles_data.yaml"
 UNDERCLOUD_ROLES_FILE = "roles_data_undercloud.yaml"
-UNDERCLOUD_OUTPUT_DIR = os.path.join(os.environ.get('HOME'),
-                                     '.undercloud-heat-installer')
+UNDERCLOUD_OUTPUT_DIR = os.path.join(os.environ.get('HOME'))
 OVERCLOUD_NETWORKS_FILE = "network_data.yaml"
 RHEL_REGISTRATION_EXTRACONFIG_NAME = (
     "extraconfig/pre_deploy/rhel-registration/")