Revert TCP checks for recovery (closes #711)

Requires more tests on Windows with serial communications...
Related to db1cbc5 and 9b679b7.

Author: stephane

src/modbus.c

@@ -449,7 +449,6 @@ int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
 #ifdef _WIN32
             wsa_err = WSAGetLastError();
             if ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
-                (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_TCP) &&
                 (wsa_err == WSAENOTCONN || wsa_err == WSAENETRESET ||
                  wsa_err == WSAENOTSOCK || wsa_err == WSAESHUTDOWN ||
                  wsa_err == WSAECONNABORTED || wsa_err == WSAETIMEDOUT ||
@@ -459,7 +458,6 @@ int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
             }
 #else
             if ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
-                (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_TCP) &&
                 (errno == ECONNRESET || errno == ECONNREFUSED || errno == EBADF)) {
                 int saved_errno = errno;
                 modbus_close(ctx);