Remove redundant calls: variable_get('user_pictures', 0) in user.admin.inc

Problem/Motivation

While debugging this issue: #2509188: The directory public://pictures does not exist or is not writable., I noticed a slight inefficiency in the user_admin_settings() function. The variable_get('user_pictures', 0) code is called twice where it could only be called once.

Remaining tasks

Review patch.