ASSERT callback.c:1478 get_app_pc_from_intercept_pc not finding pc on burst_static test

This happened 2x in a row with PR 4485:

https://ci.appveyor.com/project/DynamoRIO/dynamorio/builds/35693375
https://ci.appveyor.com/project/DynamoRIO/dynamorio/builds/35693164
```
[00:22:23] 219:
[00:22:23] 218/254 Test #219: code_api|tool.drcacheoff.burst_static ........................***Failed 0.99 sec
[00:22:23] Running cmd |C:/projects/dynamorio/build/build_debug-internal-64/clients/bin64/tool.drcacheoff.burst_static.exe|
[00:22:23] CMake Error at C:/projects/dynamorio/suite/tests/runmulti.cmake:106 (message):
[00:22:23] *** cmd failed (-1): pre-DR init
[00:22:23]
[00:22:23] pre-DR start
[00:22:23]
[00:22:23] OUT 2>&1
% grep Error OUT
% grep -c 'all done' OUT
150
```

It then went away with the s/eax/ebx/ fix: but it's not clear that's really
related or its non-deterministic in some other way, or whether it's
completely unrelated to that PR and is some latent underlying issue.
Without a reproducer we'll file it and see if it happens again.