tests: added full GC cycle operations to avoid false positives in the "check leak" test mode.

Author: agentzh

t/004-require.t

@@ -35,6 +35,7 @@ __DATA__
     location /load {
         content_by_lua '
             package.loaded.foo = nil;
+            collectgarbage()
             local foo = require "foo";
             foo.hi()
         ';

t/035-gmatch.t

@@ -440,6 +440,7 @@ done
     location /main {
         content_by_lua '
             package.loaded.foo = nil
+            collectgarbage()
 
             local res = ngx.location.capture("/t")
             if res.status == 200 then