Re-activated implicit cfs SFD test

Issue/feature addressed

The ImplicitSolverCallsSFD test, part of the CompressibleFlowSolver, was taking an excessive amount of time to run (in excess of an hour), after some recent changes to the code.

Proposed solution

Re-added the SFD test for implicit cfs Maybe in the future we can add the time check for tests?

Implementation

Since the difusionIP is fixed, the restart file for the SFD test is updated such that the test can finished quckly We therefore re-actived this test.

Tests

ImplicitSolverCallsSFD

Notes

Please add any other information that could be useful for reviewers.

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).

Warning

On the 19.07 the code formatting (code style) was standardised using clang-format, over the whole Nektar++ code. This means changes in your branch will conflict with formatting changes on the master branch. To resolve these conflicts , see #295 (closed)

Closes #123 (closed)