hail: add an extra safety check in relocate
hail: add an extra safety check in relocate

If we select the primary as new secondary, better to fail than return
wrong data to Ganeti.

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
(cherry picked from commit f25508bef4e85032f0468e5a6f0f8930ff154e66)

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

ganeti-github-testing/ganeti-test-1,apyrgio/snf-ganeti,ganeti/ganeti,ganeti/ganeti,apyrgio/ganeti,yiannist/ganeti,andir/ganeti,andir/ganeti,yiannist/ganeti,mbakke/ganeti,onponomarev/ganeti,apyrgio/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,dimara/ganeti,leshchevds/ganeti,mbakke/ganeti,bitemyapp/ganeti,grnet/snf-ganeti,dimara/ganeti,bitemyapp/ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,yiannist/ganeti,leshchevds/ganeti,onponomarev/ganeti,mbakke/ganeti,grnet/snf-ganeti,leshchevds/ganeti