PID mesh adaptation quick fix

[mivaia]

Initialized previous_mesh_controller and previous number of elements to 0 in the constructor of the mesh controller object.

Description

previous_mesh_control_error which controls the intregral part of the error was not initialized. This affected geatly the PID controller convergence because really high values would sometimes be attributed at start to previous_mesh_control_error.

Solution

Initialized the value in the constructor.

Testing

Old tests were kept.

Documentation

Miscellaneous (will be removed when merged)

Checklist (will be removed when merged)

See this page for more information about the pull request process.

Code related list:

• All in-code documentation related to this PR is up to date (Doxygen format)
• Lethe documentation is up to date
• Fix has unit test(s) (preferred) or application test(s), and restart files are in the generator folder
• The branch is rebased onto master
• Changelog (CHANGELOG.md) is up to date
• Code is indented with indent-all and .prm files (examples and tests) with prm-indent

Pull request related list:

• Labels are applied
• There are at least 2 reviewers (or 1 if small feature) excluding the responsible for the merge
• If this PR closes an issue or is related to a project, it is linked in the "Projects" or "Development" section
• If the fix is temporary, an issue is opened
• The PR description is cleaned and ready for merge