UI: Fixed position of confirm modal when scrolled down, Fixes #1345

src/css/less/grafana.less

@@ -66,7 +66,7 @@
   right: 0;
   margin-left: auto;
   margin-right: auto;
-  top: 200px;
+  top: 30%;
 }
 
 .grafana-search-metric-actions {

src/vendor/bootstrap/less/modals.less

@@ -22,7 +22,7 @@
 
 // Base modal
 .modal {
-  position: absolute;
+  position: fixed;
   z-index: @zindexModal;
   width: 100%;
   background-color: @white;