ovsdb-idl: log error in client when db schema does not exist on server
A common error scenario with OVN is to attempt to use ovn-nbctl when
the OVN databases have not been created in ovsdb-server:
1. ovn-nbctl sends "get_schema" request for OVN db to ovsdb-server.
2. ovsdb-server fails to find requested db, sends error response
to ovn-nbctl.
3. ovn-nbctl receives the error response in ovsdb_idl_run(), but
takes no specific action.
4. ovn-nbctl hangs forever in IDL_S_SCHEMA_REQUESTED state (assuming
a timeout wasn't requested on the command line).
Add a log message to inform the user of this situation.
Signed-off-by: Lance Richardson <lrichard@redhat.com> Signed-off-by: Ben Pfaff <blp@ovn.org>