The TestLldbPython test is known to fail with very old lldb releases
(3.8 and older). Skip the test when the lldb found on the system is
too old.

Fixes #22299

Change-Id: I8f78d6c0d995118f806dae87f3f04a9726473116
Reviewed-on: https://go-review.googlesource.com/c/139397Reviewed-by: Ian Lance Taylor <iant@golang.org>