Prevent file overwrite with restart for the Isentropic Vortex solver

Issue/feature addressed

Prevent the overwrite of the restart file when using the Isentropic Vortex Solver.

Proposed solution

Implementation

Tests

Suggested reviewers

Please suggest any people who would be appropriate to review your code.

Notes

The proposed approach is similar to the one adopted for MR !1540 (merged).

Checklist

• [ ] Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• [ ] Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• [ ] License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).