Add exception handling when a cached FDO connection is being removed from the cache

[brucedechant]

There is no exception handling when a FDO connection is closed while attempting to remove it from the cache. If an exception occurs during the closing of a FDO connection for whatever reason the FDO connection is not removed from the cache.

If the closing of the FDO connection fails the FDO connection should still be removed from the cache.

Examples of why the closing of a FDO connection might cause an exception:

• The underlying feature source of the FDO connection has terminated the connection on its own by a DBA
• A network cable is unplugged and the connection is lost