This count gets incremented after init succeeds, when it should be
incremented after *alloc* succeeds. Otherwise, we leak the context on
failure.
There are no negative consequences of incrementing for
allocated-but-not-initialized contexts, as the only functions that
reference it will, in the worst case, simply behave as if called on
allocated-but-not-initialized contexts, which is in line with expected
behavior when sws_init_context() fails.