mpi/pmix: Avoid extra nodeid-nodename resolutions

Improves ping-pong latency test results:

size    UCXv2   UCXv3
1       30      25
2       30      25
4       30      25
8       30      26
16      30      26
32      31      26
64      31      27
128     31      27
256     32      28
512     33      28
1024    33      28
2048    34      30
4096    37      32
8192    42      38
16384   45      42
32768   52      47
65536   64      59
131072  88      83
262144  2248    2224
524288  2879    2782
1048576 3770    3624
2097152 6234    6135
4194304 10473   10427

Signed-off-by: Artem Polyakov <artpol84@gmail.com>