Fix unit test fixes

Complete the fixes for !1489 (merged). Please note that this MR isn't directed towards the master, but to the branch unit_test_fixes.

• applied code formatting tool
• in testGravitySpeed.c: changed engine.ti_current to = 1 so that gparts pass cell_are_gparts_drifted check in runner_dopair_grav_pp() call with --enable-debugging-checks on