Undo part of the recent cache-deactivation for attribute definitions
When all calls for "db_attribute_defined" are performed without caching, this results in a huge amount of additional SQL queries, since these tests are performed during blueprint definition as well during every blueprint reload of every db attribute. On a small site with just 6 connection threads (2 monitor, 2 default, 2 slow), this results during startup with 969 additional SQL queries, a reload of xowiki causes an additional 1063 of such queries. When a site defines much more connection threads ((the LEARN site has e.g. 85 connection threads defined), these DB attribute testing operations will result in 10K+ of mostly useless SQL queries. As a consequence of this, the startup of the server will become slower, reloads will become slower etc., which is bad especially for large sites.
The new implementation seems to fix the original problem case (running xotcl_core_tutorial_4 multiple times). If there is still a problem with installing xolp [2] this problem should be analyzed and fixed probably there. If necessary, a proper bug report would be appreciated to reduce guessing work.