tests: Actually wait until message is sent on send_message.

Previously, using e.g. the search box would be problematic because the
compose box closing event might fire, blurring the search box, in the
middle of whatever you were doing.

(imported from commit cc045f5a6a7b7fbf72848da14b6fcd3df39cab05)

zephyr/tests/frontend/tests/01-site.js

@@ -74,6 +74,7 @@ function send_message(type, params) {
     casper.click('#left_bar_compose_' + type + '_button_big');
     casper.fill('form[action^="/json/send_message"]', params);
     casper.click('#compose-send-button');
+    casper.waitWhileVisible('#compose');
 }
 
 // Wait for any previous send to finish, then send a message.