usrloc: refactor some db queries using global usrloc_columns variable

[lbalaceanu]

Pre-Submission Checklist

• [x] Commit message has the format required by CONTRIBUTING guide
• [x] Commits are split per component (core, individual modules, libs, utils, ...)
• [x] Each component has a single commit (if not, squash them into one commit)
• [x] No commits to README files for modules (changes must be done to docbook files in doc/ subfolder, the README file is autogenerated)

Type Of Change

• [ ] Small bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds new functionality)
• [ ] Breaking change (fix or feature that would change existing functionality)

Checklist:

• [ ] PR should be backported to stable branches
• [ ] Tested changes locally
• [ ] Related to issue #XXXX (replace XXXX with an open issue number)

Description

This is a refactor aiming to make some queries that return most of the columns of contacts easier to read. Gets rid of repeating local columns arrays and replaces them with a single global usrloc_columns variable. Similar change was done for p_usrloc module.