Fix for parallel strong scalar bcs in parallel for the case where all owned nodes in a domain are on the strong bc boundary.
Fix for parallel strong scalar bcs in parallel for the case where all owned nodes in a domain are on the strong bc boundary.

This might fix the hangs in square-convection-parallel-trivial (it fixes at least some of them).

FluidityProject/multifluids,FluidityProject/multifluids,FluidityProject/multifluids,FluidityProject/multifluids