Remove buggy b/c logic in Parser::disableCache()/updateCacheExpiry()

Remove buggy b/c logic in Parser::disableCache()/updateCacheExpiry()

* Setting mCacheTime to -1 is for old callers that
  only check getCacheTime() instead of getCacheExpiry().
  Most of them are already broken (WikiLog/SemanticForms) as
  they check for -1 which is in fact never returned
  due to the TS_MW conversion in Parser::getCacheTime.
* By using -1, the value of page_links_updated can end up
  as 1969, which is confusing and broken.

Change-Id: I8809a4258eacff05992a2c27ade7f6a0c1731c51