travis: switch to using root user

When I pushed the last change, I noticed that Travis was beginning
to fail due to db permission errors. This is a trivial fixup.

Signed-off-by: Daniel Axtens <[email protected]>
(cherry picked from commit 10a132f)

Author: daxtens

.travis.yml

@@ -12,7 +12,7 @@ services:
 
 env:
   global:
-    - PW_TEST_DB_USER=travis
+    - PW_TEST_DB_USER=root
     - PW_TEST_DB_PASS=""
     - PW_SKIP_BROWSER_TESTS=yes