It's accidentally broken when refactoring the testdata path. Also clean
up the testcase a bit by simplying the file reading.
Test: recovery_unit_test passes.
Change-Id: I592a1cf5a4eb9a7a5f4eecbc6426baeedeb02781
Clean up the duplicated codes that handle the zip files in
bootable/recovery; and rename the library of the remaining
utility functions to libotautil.
Test: Update package installed successfully on angler.
Bug: 19472796
Change-Id: Iea8962fcf3004473cb0322b6bb3a9ea3ca7f679e