Disable MSYS path conversion for Bazel integration tests as part of test setup; remove this from individual integration tests.

This prevents issues like https://stackoverflow.com/questions/48953956/building-bazel-on-a-windows-machine/49004265 for Windows integration tests.

PiperOrigin-RevId: 676022619
Change-Id: I8405baede1a2722505dcf65fc8d10c6e16a723a2