improve http error handling

Description

little improvement for easy vista provider http return code

[x] Patch fixing an issue (non-breaking change)
[ ] New functionality (non-breaking change)
[ ] Breaking change (patch or feature) that might cause side effects breaking part of the Software

[ ] I have followed the coding style guidelines provided by Centreon
[ ] I have commented my code, especially new classes, functions or any legacy code modified. (docblock)
[ ] I have commented my code, especially hard-to-understand areas of the PR.
[ ] I have rebased my development branch on the base branch (master, maintenance).