Don't do recovery operations under Empty/AttributeError

Don't do recovery operations under Empty/AttributeError

Made some adjustments to :class:`.Pool` and :class:`.Connection` such
that recovery logic is not run underneath exception catches for
``pool.Empty``, ``AttributeError``, since when the recovery operation
itself fails, Python 3 creates a misleading stack trace referring to the
``Empty`` / ``AttributeError`` as the cause, when in fact these exception
catches are part of control flow.

Change-Id: Id3ed9a8f96ce4ccb4009c94af30ddc2ddb9818b9
Fixes: #4028