fix useless permission required and improve perf for mssql db size mode

[tanguyvda]

Community contributors

Description

• remove the USE $database because the query after that doesn't require us to be inside the database
• move the database size query outside of the for loop because it makes no sens to run it for every database when said query returns the size of each database anyway

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Functionality enhancement or optimization (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software

How this pull request can be tested ?

I have no clue

Checklist

• I have followed the coding style guidelines provided by Centreon
• I have commented my code, especially hard-to-understand areas of the PR.
• I have rebased my development branch on the base branch (develop).
• I have provide data or shown output displaying the result of this code in the plugin area concerned.