selftests: net/rds: add module not found

This fix solves this error, when calling kselftest with targets "net/rds":

The error was found by running tests manually with the command:
make kselftest TARGETS="net/rds"

The patch also specifies to import ip() function from the utils module.

Signed-off-by: Alessandro Zanni <[e-mail]>
Reviewed-by: Allison Henderson <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/rds/test.py

···
 import atexit
 from pwd import getpwuid
 from os import stat
-from lib.py import ip
 
+# Allow utils module to be imported from different directory
+this_dir = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(this_dir, "../"))
+from lib.py.utils import ip
 
 libc = ctypes.cdll.LoadLibrary('libc.so.6')
 setns = libc.setns