Contract test for renaming over existing file is too lenient

AbstractContractRenameTest#testRenameFileOverExistingFile is too lenient in its assertions.

• FileAlreadyExistsException is accepted regardless of "rename overwrites" and "rename returns false if exists" contract options. I think it should be accepted only if both of those options are false.
• "rename returns false if exists" option is ignored if the file is not overwritten by the implementation.

Also, I think the "rename returns false if exists" option is incorrectly inverted in the test, which it can get away with because the checks are loose.

(Found this while looking at a change in Ozone FS implementation from throwing exception to returning false. The contract test unexpectedly passed without changing contract.xml.)