Fix install O2 on subcloud failed

Fix install O2 on subcloud failed

The O2 application installation on a subcloud will fail because the
default region name is "RegionOne," while the subcloud has a different
region name.

This commit adds an environment variable that allows the user to set the
region name, replacing the default one.

Test Cases:

1. Successfully installed the O2 application on the subcloud.
2. Successfully installed the O2 application on the central cloud.

Issue-ID: INF-467

Change-Id: I893680b8c2519667b1784b751950ea8a3f14cbce
Signed-off-by: Zhang Rong(Jon) <rong.zhang@windriver.com>