autotest-gwt: set no cache header on all pages

Not sure this will solve the caching issue ( I can not recreate) but I do
believe it will do any harm.

TEST=build and tested the gwt/ui

Change-Id: Iac38b4e5c258a605c3f4eb0e00ab025df031c33b
diff --git a/third_party/autotest/apache/conf/all-directives b/third_party/autotest/apache/conf/all-directives
index 2b21cfa..7a69981 100644
--- a/third_party/autotest/apache/conf/all-directives
+++ b/third_party/autotest/apache/conf/all-directives
@@ -4,6 +4,13 @@
 
 DocumentRoot /usr/local/autotest/apache/www/
 
+<FilesMatch "\.*\.*">
+    <IfModule mod_headers.c>
+        Header set Cache-Control "no-cache, must-revalidate"
+    </IfModule>
+</FilesMatch>
+
+
 Include "/usr/local/autotest/apache/conf/logging-directives"
 Include "/usr/local/autotest/apache/conf/cgi-directives"
 Include "/usr/local/autotest/apache/conf/gwt-directives"