handle asyncpg InternalClientError

Fixed issue where the asyncpg driver could throw an insufficiently-handled
exception ``InternalClientError`` under some circumstances, leading to
connections not being properly marked as invalidated.

Fixes: #13241
References: https://github.com/MagicStack/asyncpg/issues/1069
Change-Id: Iaaf551b3d7b062cce62e13b441161583a484615f