Init APR so that the Serf fetcher's SSL code can init without crashing in APR pool code.

This isn't needed in Apache since it of course inited APR itself (and our Serf unit tests call apr_initialize() as well).

The other uses within Serf + nginx manage to not crash since they specify an allocator to their use of apr_pool_create[_ex] which avoids trying to look one up from the global pool. 

The main question here is whether timing is correct.