fix(toolbar): add border-top when toolbar is positioned to the bottom

fixes #5967

Author: brandyscarney

ionic/components/toolbar/toolbar.ios.scss

@@ -42,7 +42,7 @@ ion-navbar-section {
 
 .toolbar-background {
   border-bottom-width: 1px;
-  border-bottom-style: solid;
+  border-style: solid;
   border-color: $toolbar-ios-border-color;
   background: $toolbar-ios-background;
 }
@@ -51,6 +51,15 @@ ion-navbar-section {
   border-bottom-width: $hairlines-width;
 }
 
+.toolbar[position=bottom] .toolbar-background {
+  border-bottom-width: 0;
+  border-top-width: 1px;
+}
+
+&.hairlines .toolbar[position=bottom] .toolbar-background {
+  border-top-width: $hairlines-width;
+}
+
 
 // iOS Toolbar Content
 // --------------------------------------------------