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.
This line and the next line should be removed since it can't be supported. I believe it should be replaced with "default credentials used by Pulp" since not having username and password set in the conf file causes the default to be used.