kernel-test: verify REMOTE_NAME and URL
If the checked out git repository already has a remote with the name
KERNEL_REMOTE_NAME, make sure that the KERNEL_URL matches the remote
URL.
Motivation for this change is osmo-ci
I5d4202a67a24d9c15a5b211fa29ce9d5b5a9d9c1, which will expose the
parameters in the jenkins job.
Related: OS#3208
Change-Id: I18b29011e3e8e2577bdf1a9c64c4370309cc8399
