[wp] avoid test to use cache

src/plugins/wp/tests/wp_plugin/stmt.c

 /* run.config
-   OPT: -load-module report -then -report 
+   OPT: -load-module report -then -report
 */
 
 /* run.config_qualif
-   OPT: -load-module report -then -report 
-   EXECNOW: LOG stmt.log LOG f.dot LOG f_default_for_stmt_2.dot LOG g.dot LOG g_default_for_stmt_11.dot @frama-c@ -no-autoload-plugins -load-module wp -wp-precond-weakening -wp -wp-model Dump -wp-out tests/wp_plugin/result_qualif @PTEST_FILE@ 1> tests/wp_plugin/result_qualif/stmt.log
+   OPT: -load-module report -then -report
+   EXECNOW: LOG stmt.log LOG f.dot LOG f_default_for_stmt_2.dot LOG g.dot LOG g_default_for_stmt_11.dot @frama-c@ -no-autoload-plugins -load-module wp -wp-precond-weakening -wp -wp-model Dump -wp-out tests/wp_plugin/result_qualif -wp-cache none @PTEST_FILE@ 1> tests/wp_plugin/result_qualif/stmt.log
 */
 
 /*@ ensures a > 0 ==> \result == a + b;