Use libmesh_cppunit.h in new unit tests
Use libmesh_cppunit.h in new unit tests

This saves a few lines of boilerplate and fixes a compilation failure
with float128.

BalticPinguin/libmesh,hrittich/libmesh,hrittich/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,hrittich/libmesh,roystgnr/libmesh,libMesh/libmesh,dschwen/libmesh,roystgnr/libmesh,jwpeterson/libmesh,roystgnr/libmesh,libMesh/libmesh,dschwen/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,BalticPinguin/libmesh,libMesh/libmesh,capitalaslash/libmesh,hrittich/libmesh,capitalaslash/libmesh,dschwen/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,hrittich/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,roystgnr/libmesh,libMesh/libmesh,capitalaslash/libmesh,hrittich/libmesh,hrittich/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,libMesh/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,capitalaslash/libmesh,dschwen/libmesh,roystgnr/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,hrittich/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,libMesh/libmesh,roystgnr/libmesh,roystgnr/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,hrittich/libmesh