Install Guide: Fix PASS/DBPASS usage

X_DBPASS is the MySQL password, X_PASS the keystone service one.
Fix places that used DBPASS instead of PASS.

Change-Id: Icf210e4d1c51b74897e9dc8fbabe53968d4b2e2c
backport: havana
fixing several style nits in ch_identity_mgmt.xml

Change-Id: Ifdf2ffb9705ef4fa9894e60a8757e87bf90997d5
Merge "Install Guide: Fix PASS/DBPASS usage"
Merge "fixing several style nits in ch_identity_mgmt.xml"