Bug 1159067 - Read user cred from config

Bug 1159067 - [RFE] allow pulp to read user credentials from users admin.conf
if he/she does not want to provide password on command prompt
or --password in pulp-admin

this is basically for writing a batch job that would include multiple command lines together.
The imports below that start with pup.* should be in their own group with a space separating them. See [PEP8 Imports](http://legacy.python.org/dev/peps/pep-0008/#imports) for more about this.