Fix flaky test

Waiting for the timeout option to be set means we could still sneak in
and grab the old FDB database handle before fabric2_server updated it in
the application environment.

This new approach just waits until the handle has been updated by
watching the value in the application environment directly.
diff --git a/src/fabric/test/fabric2_tx_options_tests.erl b/src/fabric/test/fabric2_tx_options_tests.erl
index b93cc3d..3232922 100644
--- a/src/fabric/test/fabric2_tx_options_tests.erl
+++ b/src/fabric/test/fabric2_tx_options_tests.erl
@@ -84,9 +84,15 @@
 
     meck:reset(erlfdb),
 
+    % Wait until after fabric2_server has updated the new fdb handle
+    OldDbHandle = get(?PDICT_DB_KEY),
     config:delete("fdb_tx_options", "size_limit", false),
-    % Assert that we get a new handle and are setting our default values
-    meck:wait(erlfdb, set_option, ['_', timeout, '_'], 4000),
+    test_util:wait(fun() ->
+        case application:get_env(fabric, db) of
+            {ok, OldDbHandle} -> wait;
+            {ok, _} -> ok
+        end
+    end),
     erase(?PDICT_DB_KEY),
 
     {ok, Db1} = fabric2_db:open(DbName, [?ADMIN_CTX]),