test: call setUrlString for memcached plugin only when it is required.

this commit prevents generating needless activities at the beginning of tests.
retrieve url/port from ZopeTestCase utils
Git.getRemoteUrl() returns pushurl if exists, else url.
remove View permission for Anonymous in discussion_thread_module.

because the list of threads for Anonymous should be provided through predicate in Web Section, not from the module itself.
Stop initializing 'serverhost' & 'serverport' on the testcase class.

It was unreliable because done only for the first test.
Code needing this information can simply call startZServer, which will simply
return host/port of already started ZServer.
BusinessTemplate: Kill fillRecursivePathList.