Fixed user dropdown alignment

LEARNER-741

lms/static/sass/base/_layouts.scss

@@ -18,6 +18,10 @@ body.view-in-course {
 
     .wrapper-header {
       min-width: auto;
+
+      .user-dropdown, .dropdown {
+        padding: ($baseline/2);
+      }
     }
   }
 

lms/static/sass/shared/_header.scss

@@ -185,7 +185,7 @@
 
     .user-dropdown, .dropdown {
       font-size: $body-font-size;
-      padding: 0 ($baseline/2);
+      padding: ($baseline/4) ($baseline/2);
       color: $base-font-color;
       border: none;
       background: $white;