FS-10395: [mod_sofia] Fix ssl error handling in tls sip traffic

Clears SSL error state.

Updates tport_tls.c to clear the SSL error state after an error occurs.

OpenSSL puts errors into a queue that is kept in thread local storage.
In some cases, such as when SSL_ERROR_SSL is returned by SSL_get_errror(),
OpenSSL will queue multiple errors for a single event. When this occurs,
OpenSSL will report an error the next time I/O is performed if the queue
is not cleared first, which can result in TLS connections being torn down
prematurely.

libs/sofia-sip/libsofia-sip-ua/tport/tport_tls.c

@@ -769,6 +769,7 @@ int tls_error(tls_t *tls, int ret, char const *who,
     return 0;
 
   case SSL_ERROR_SYSCALL:
+    ERR_clear_error();
     if (SSL_get_shutdown(tls->con) & SSL_RECEIVED_SHUTDOWN)
       return 0;			/* EOS */
     if (errno == 0)
@@ -897,7 +898,7 @@ ssize_t tls_write(tls_t *tls, void *buf, size_t size)
   tls->write_events = 0;
 
   ret = SSL_write(tls->con, buf, size);
-  if (ret < 0)
+  if (ret <= 0)
     return tls_error(tls, ret, "tls_write: SSL_write", buf, size);
 
   return ret;
@@ -1020,6 +1021,8 @@ int tls_connect(su_root_magic_t *magic, su_wait_t *w, tport_t *self)
           if ((su_wait_create(wait, self->tp_socket, self->tp_events) == -1) ||
              ((self->tp_index = su_root_register(mr->mr_root, wait, tport_wakeup,
                                                            self, 0)) == -1)) {
+
+            tls_log_errors(3, "TLS post handshake error", status);
             tport_close(self);
             tport_set_secondary_timer(self);
 	    return 0;
@@ -1041,12 +1044,7 @@ int tls_connect(su_root_magic_t *magic, su_wait_t *w, tport_t *self)
 	break;
 
       default:
-        {
-	  char errbuf[64];
-	  ERR_error_string_n(status, errbuf, 64);
-          SU_DEBUG_3(("%s(%p): TLS setup failed (%s)\n",
-					  __func__, (void *)self, errbuf));
-        }
+        tls_log_errors(3, "TLS setup failed", status);
         break;
     }
   }