(test cleanup) Add subtest to TestInitRAMFS
(test cleanup) Add subtest to TestInitRAMFS

TestInitRAMFS tests two different files ("testdata/bzImage", "testdata/bzimage-64kurandominitramfs") - when one of those tests fails it's not obvious which one has failed, and if the first test fails then the second test does not run.

Let's modify the test structure such that it uses subtests. Now the name of each file is listed in any test failures and both tests will run, even if the first fails.

Sample output showing the failing file names in the test output: https://gist.github.com/abrender/6d70872c1fd9a9afb8ff703aad0b5980

Signed-off-by: Avi Brender <11ee27df373bbd309e6724095478ce22858b8ef0@google.com>

u-root/u-root,u-root/u-root,u-root/u-root