Remove remnants of blocking DTLS timeouts.

We only support non-blocking BIOs for DTLS as of
https://boringssl-review.googlesource.com/13945. This logic is a remnant
of that. It should not be necessary. All users of DTLSv1_get_timeout
call DTLSv1_handle_timeout. This gets it out of the way for
dtls_open_record calls which don't use dtls1_get_record.

We can restore it elsewhere if necessary, but I don't think we need it.

Change-Id: Idb737868358e4b59ad3cb2c994c7084ffcdb3709
Reviewed-on: https://boringssl-review.googlesource.com/21349
Commit-Queue: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Steven Valdez <svaldez@google.com>

ssl/d1_pkt.cc

@@ -143,18 +143,6 @@ again:
   // Read a new packet if there is no unconsumed one.
   if (ssl_read_buffer(ssl).empty()) {
     int read_ret = ssl_read_buffer_extend_to(ssl, 0 /* unused */);
-    if (read_ret < 0 && dtls1_is_timer_expired(ssl)) {
-      // Historically, timeouts were handled implicitly if the caller did not
-      // handle them.
-      //
-      // TODO(davidben): This was to support blocking sockets but affected
-      // non-blocking sockets. Can it be removed?
-      int timeout_ret = DTLSv1_handle_timeout(ssl);
-      if (timeout_ret <= 0) {
-        return timeout_ret;
-      }
-      goto again;
-    }
     if (read_ret <= 0) {
       return read_ret;
     }