db: drop the obfuscation of database password

Added support for the new configuration structure
for database related parameters.
If the new configuration structure can't be found
fallback to legacy pg_pass file.
Don't ask the DB password if already read from
configuration files.

Change-Id: I763f5a9d1d3307ee384281b13db5c6c9436060df
Bug-Url: https://bugzilla.redhat.com/958532
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>