Set correctly UCX_TLS

[dcesari]

When using hpcx-openmpi/2.9.0 and asking for ~10 or more nodes for an MPI program with the default configuration we get an error at MPI setup time, which disappears by setting export UCX_TLS=all instead of the default

module load hpcx-openmpi/2.9.0
ucx_info -c | grep UCX_TLS
UCX_TLS=rc_x,self,sm

but this could not be the ideal setting, User Support suggested export UCX_TLS=dc_x,self,sm, however we should verify that this does not impair performance. See also openucx/ucx#7978