Fix Sidecars Show Messages Button

By default all Beats collectors prefix our fields with "fields_".
Adjust the search accordingly.
Fixes #5045

graylog2-web-interface/src/components/sidecars/sidecars/SidecarRow.jsx

@@ -70,7 +70,7 @@ class SidecarRow extends React.Component {
             <LinkContainer to={`${Routes.SYSTEM.SIDECARS.ADMINISTRATION}?node_id=${sidecar.node_id}`}>
               <Button bsSize="xsmall" bsStyle="info">Manage sidecar</Button>
             </LinkContainer>
-            <LinkContainer to={Routes.search_with_query(`gl2_source_collector:${sidecar.node_id}`, 'relative', 604800)}>
+            <LinkContainer to={Routes.search_with_query(`fields_gl2_source_collector:${sidecar.node_id}`, 'relative', 604800)}>
               <Button bsSize="xsmall" bsStyle="info">Show messages</Button>
             </LinkContainer>
           </ButtonToolbar>