mysqlds: add placeholder/typeahead for localhost connection strings

for the host field on the data source config page. Fixes #9046

public/app/plugins/datasource/mysql/partials/config.html

@@ -4,7 +4,7 @@
 <div class="gf-form-group">
 	<div class="gf-form max-width-30">
 		<span class="gf-form-label width-7">Host</span>
-		<input type="text" class="gf-form-input" ng-model='ctrl.current.url' placeholder="" required></input>
+		<input type="text" class="gf-form-input" ng-model='ctrl.current.url' placeholder="localhost:3306" bs-typeahead="{{['localhost:3306', 'localhost:3307']}}" required></input>
 	</div>
 
 	<div class="gf-form max-width-30">