fix for cases where connection is broken and release() is called, avo…

[olgkpln]

Fixing a case when release() is called for a broken connection. without this, the broken connection is returned to the idle pool and reused.

[brianc]

Thanks for the pull request @olgkpln! Any way you could write a test for this?

[johanneswuerbach]

I think https://github.com/brianc/node-pg-pool/pull/115 is a better way to prevent this or is there any other way then double releasing the client to trigger this bug?

[brianc]

ah yeah if #115 fixes this I can just merge that one.

[olgkpln]

#115 is a good fix as well