Improve error reporting in RateLimitTest

This change moves the logic to read /proc/config.gz from the static
initializer to a function that runs the first time setUp is called. This
improves error reporting as exceptions thrown inside
ensureKernelConfigLoaded get reported as test failures.

Test: atest RateLimitTest
Change-Id: I3b7913c567507dec8ecad26602cfccdad3d6f4bd
1 file changed