This change adds the admin_password to the mask_fields in the
settings.py file, in order to prevent this password from being logged in
plain text.
Test Plan:
PASS: Apply this change and verify that in every user password change,
the admin_password is masked.
Closes-bug: 2058294
Signed-off-by: Enzo Candotti <enzo.candotti@windriver.com>
Change-Id: Iba80d682e7bd74c0903dd2f23334f3298229cb2e