ticket:8464: If LRUCache constructor fails, make sure destructor will still work.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@34673 251d0590-4201-4cf1-90de-194747b24ca1
ticket:8464: RelativeDateFormatter tests now passing for C++

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@34674 251d0590-4201-4cf1-90de-194747b24ca1