MueLu: signed/unsigned comparison warning in master

Created by: mhoemmen

@vbrunini reports a signed-unsigned comparison build error in Trilinos:master, in packages/muelu/src/Transfers/Smoothed-Aggregation/MueLu_TentativePFactory_def.hpp:193:

.../MueLu_TentativePFactory_def.hpp: In instantiation of 'void MueLu::TentativePFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::BuildP(MueLu::TentativePFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Level&, MueLu::TentativePFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Level&) const [with Scalar = double; LocalOrdinal = int; GlobalOrdinal = long int; Node = Kokkos::Compat::KokkosDeviceWrapperNode<Kokkos::Serial>; MueLu::TentativePFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Level = MueLu::Level]':
    [REDACTED]:   required from here

.../MueLu_TentativePFactory_def.hpp:193:34: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
             for (LO lnode = 0; lnode < numNodes; lnode++) {

@trilinos/muelu