ActionWarehouse holds MooseSharedPointer<MooseMesh> instead of MooseMesh*

It provides access to _mesh and _displaced_mesh for other parts of the
code like SetupMeshAction:act() and MooseApp::meshOnly(), that are
actually responsible for constructing the Mesh object.  This means
that other objects, like FEProblem, are no longer responsible for
deleting the Mesh.

See also #3446
Adding some valgrind suppressions for openmpi

Refs #3547