Fix TLS write busy-spin on SSL_ERROR_WANT_READ

A TLS sendData() failing with SSL_ERROR_WANT_READ (mid-handshake
application data, or a post-handshake session ticket exchange) has
nothing to do with write-readiness, but resetSocket() kept re-arming
EPOLLWRNORM anyway - an already-writable TCP socket fires that
immediately, so the retry loop spun the CPU as fast as it could
until the connection was eventually dropped, without ever reading
the peer's first command. Confirmed via a 15GB+ debug log from one
stuck connection. sendNeedsRead() lets Socket now tell the
difference and wait for a real EPOLLIN instead of busy-retrying.

TLS.cpp

@@ -251,15 +251,18 @@ namespace core {
 
       if((len = ::SSL_write(ssl, data, length)) >= 0) {
 	 coreutils::Log(coreutils::LOG_DEBUG_3) << "sendData TLS...len=" << len;
+	 lastSendWantedRead = false;
 	 return len;
       }
       else {
+	 lastSendWantedRead = false;
 	 switch (SSL_get_error(ssl, len)) {
 	  case SSL_ERROR_SSL:
 	    coreutils::Log(coreutils::LOG_DEBUG_3) << "ERROR_SSL on ssl_write. error=" << errno;
 	    break;
 	  case SSL_ERROR_WANT_READ:
 	    coreutils::Log(coreutils::LOG_DEBUG_3) << "ERROR_WANT_READ on ssl_write.";
+	    lastSendWantedRead = true;
 	    break;
 	  case SSL_ERROR_WANT_WRITE:
 	    coreutils::Log(coreutils::LOG_DEBUG_3) << "ERROR_WANT_WRITE on ssl_write.";