DO NOT MERGE [CTS] Fix tests for devices that don't support backup feature

assumeTrue() is not available on JUnit3, so it got replaced with
a normal "if" check.

Test: make cts -j40 && cts-tradefed run cts -m CtsBackupHostTestCases
Bug: 63692335
Change-Id: Iaa1adbc61f2b71ad9bd2b773c9e7413e35173e36
3 files changed