vhost-user-scsi: assert() in iscsi_add_lun()

Instead of a preliminary check, add an assert to the function that has
the pre-condition.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>

contrib/vhost-user-scsi/vhost-user-scsi.c

@@ -257,6 +257,7 @@ static int iscsi_add_lun(iscsi_lun_t *lun, char *iscsi_uri)
 
     assert(lun);
     assert(iscsi_uri);
+    assert(!lun->iscsi_ctx);
 
     iscsi_ctx = iscsi_create_context(VUS_ISCSI_INITIATOR);
     if (!iscsi_ctx) {
@@ -663,11 +664,6 @@ static int vdev_scsi_add_iscsi_lun(vhost_scsi_dev_t *vdev_scsi,
     assert(iscsi_uri);
     assert(lun < VUS_MAX_LUNS);
 
-    if (vdev_scsi->luns[lun].iscsi_ctx) {
-        PERR("Lun %d already configured", lun);
-        return -1;
-    }
-
     if (iscsi_add_lun(&vdev_scsi->luns[lun], iscsi_uri) != 0) {
         return -1;
     }