Multinode tests can only be run with tcp provider

[Tomasz Gromadzki]

It is impossible to set verbs provider with -p argument as it is always overwritten by the setup_hints() function:

libfabric/fabtests/multinode/src/core_coll.c

Line 528 in 9d53956

 hints->fabric_attr->prov_name = strdup("tcp");