Fix flakey Server unit test

Change-Id: Ibc37ced6417e0174400ea6485bf9d4378df38172
Reviewed-on: http://gerrit.dmdirc.com/1038
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Shane Mc Cormack <shane@dmdirc.com>

test/com/dmdirc/ServerTest.java

@@ -37,6 +37,7 @@ public class ServerTest {
     @BeforeClass
     public static void setUp() throws Exception {
         Main.setUI(new DummyController());
+        Main.extractCorePlugins("tabcompletion_");
         IdentityManager.load();
         server = new Server(new URI("irc-test://255.255.255.255"),
                 IdentityManager.getProfiles().get(0));