Fixed bug CORE-4135 : In SS sweep blocks establishment of concurrent attachments.
More details in tracker.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58270 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed bug CORE-4134 : Race condition when auto-sweep is started

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58271 65644016-39b1-43b1-bf79-96bc8fe82c15