[postgresql] obtain PGPASSWORD from the environment

Allow the value of PGPASSWORD to be inherited from the
environment. This prevents the password being exposed in command
line parameters that may be visible to other users on the system.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
[sosreport] handle KeyboardInterrupt while importing sos

Fixes #376

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>