be_openssl: avoid leaking of SSL structure

be_openssl: avoid leaking of SSL structure

From nmathewson/Libevent#83 by @fancycode:
  There are a few code paths where the passed SSL object is not released in error cases, even if BEV_OPT_CLOSE_ON_FREE is passed as option while for others it is released. That way it's impossible for the caller to know it he has to free it on errors himself or not.

  Line numbers are from "bufferevent_openssl.c" in 911abf3:

  L1414 ("underlying == NULL" passed)
  L1416 (bio could not be created)
  L1446 (different fd passed)
  L1325 (both underlying and fd passed)
  L1328 (out-of-memory)
  L1333 ("bufferevent_init_common_" failed)
  In all error cases after the "bufferevent_ops_openssl" has been assigned, the option is evaluated on "bufferevent_free" (L1399) and the SSL object released (L1226).

Fixes: nmathewson/Libevent#83