net_ib: fix out of bounds read in ncclIbGdrSupport on non-RDMA kernel

[LunNova]

Fixes #1469

Details

Do not mention proprietary info or link to internal work items in this PR.

Work item: #1469

What were the changes?
Fixed out of bounds read and subsequent crash if none of the entries in memory_peers_path exist.

Why were the changes made?
Crashing is bad.

How was the outcome achieved?
Only crashes/demonstrates UB on a system that is missing all entries in this list.

Additional Documentation:
What else should the reviewer know?

Approval Checklist

Do not approve until these items are satisfied.

• Verify the CHANGELOG has been updated, if
  • there are any NCCL API version changes,
  • any changes impact library users, and/or
  • any changes impact any other ROCm library.

[wenkaidu]

CI failure on 4gfx908 was in docker stage.
CI failure on 16gfx90a was known issue with FP8:
[ INFO ] SP 16 ranks AllReduce (OP,GM,NL) ncclFp8E4M3 sum [ 393216 elements]
../../../test/common/TestBed.cpp:396: Failure
Expected equality of these values:
isCorrect
Which is: false
true
Output does not match expected

Thus merging the PR.