Fix dropdown z-index

client/src/sass/include/_variables.scss

@@ -175,10 +175,10 @@ $zindex: (
   popover         : 13000,
   tooltip         : 14000,
   loadbar         : 15000,
-  dropdown        : 17000,
-  help-popover    : 17000,
   privacymsg      : 17500,
   header          : 17500,
+  help-popover    : 17600,
+  dropdown        : 17600,
   modal           : 19000,
   hotkeys         : 19000,
   notification    : 20000

client/src/sass/z-index.scss

@@ -13,9 +13,9 @@ ngx-loading-bar {
   z-index: z(header) + 1 !important;
 }
 
-/* rules for dropdowns excepts when in button group, to avoid impacting the dropdown-toggle */
-.dropdown,
-.dropup {
+// Dropdown added to body, override default z-index
+body > .dropdown,
+body > .dropup {
   z-index: z(dropdown) !important;
 }