fiemap: add image_test and writer_test tests to presubmit

Add fiemap_image_test and fiemap_writer_test to TEST_MAPPING to be run
by TH as presubmits.
Because of a bug under investigation, the actual
fiemap_image_test_presubmit is used instead of the original, that has
one test case disabled.

Bug: none
Test: TH, fiemap_image_test, fiemap_writer_test
Change-Id: I63b5e69b5c245a18eceb1e5896df7bd0577f289b
Signed-off-by: Alessio Balsini <balsini@google.com>