MueLu: Scalar=float build errors

Created by: mhoemmen

@trilinos/muelu Reported by @davydden in this comment. Here are the reported build errors:

    8158    In file included from /Users/davydden/spack/var/spack/stage/trilinos-develop-p6xmhguuqtomai5fy4a36qmnn4wpqzfq/Trilinos/spack-build/packages/muelu/src/Utils/ExplicitInstantiation/MueLu_Zoltan2Interface.cpp:55:
  >> 8159    /Users/davydden/spack/var/spack/stage/trilinos-develop-p6xmhguuqtomai5fy4a36qmnn4wpqzfq/Trilinos/packages/muelu/src/Rebalancing/MueLu_Zoltan2Interface_def.hpp:197:24: error: no matching constructor for initialization of 'InputAdapterType' (aka 'XpetraMultiVe
             ctorAdapter<MultiVector<float, int, int, Kokkos::Compat::KokkosDeviceWrapperNode<Kokkos::Serial, Kokkos::HostSpace> > >')
     8160          InputAdapterType adapter(coords, weights, strides);
     8161                           ^       ~~~~~~~~~~~~~~~~~~~~~~~~
     8162    /Users/davydden/spack/var/spack/stage/trilinos-develop-p6xmhguuqtomai5fy4a36qmnn4wpqzfq/Trilinos/packages/muelu/src/Utils/MueLu_ETI_4arg.hpp:32:45: note: in instantiation of member function 'MueLu::Zoltan2Interface<float, int, int, Kokkos::Compat::KokkosDevi
             ceWrapperNode<Kokkos::Serial, Kokkos::HostSpace> >::Build' requested here
     8163      TPETRA_INSTANTIATE_SLGN_NO_ORDINAL_SCALAR(MUELU_ETI_GROUP)
     8164                                                ^
     8165    /Users/davydden/spack/var/spack/stage/trilinos-develop-p6xmhguuqtomai5fy4a36qmnn4wpqzfq/Trilinos/packages/zoltan2/src/input/Zoltan2_XpetraMultiVectorAdapter.hpp:119:3: note: candidate constructor not viable: no known conversion from 'std::vector<const double
              *>' to 'std::vector<const scalar_t *> &' (aka 'vector<const float *> &') for 2nd argument

It's possible that this could block Sierra promotion, since they enable Scalar=float.