[lldb] Remove PopPlan asserts and skip test on Arm/AArch64 Linux

This reverts commit 481bb62e and
71b4d749, along with the logging
and assert I had added to the test previously.

Now that I've caught it failing on Arm:
https://lab.llvm.org/buildbot/#/builders/17/builds/46598

Now I have enough to investigate, skip the test on the effected
platforms while I do that.