Fix osxrelocator is_mach_o_file and change_id methods
Provide object_file to is_mach_o_file in change_id and filter "ar archive" as not Mach-O files
When sending filename instead of object_file, i.e. full path to file, the command 'file -bh filename' is not able to find the file. Therefore, the function will return False always that fileext is different that '.dylib'.
ar archive files (*.a) compiled for OSX contain the string "Mach-O", however, these files are not expected to be relocated.