[DoctrineBridge] Allowing memcache port to be 0 to support memcache unix domain sockets.

[DoctrineBridge] Allowing memcache port to be 0 to support memcache unix domain sockets.

Bug fix: yes
Feature addition: no
Backwards compatibility break: no
Fixes the following tickets: #6527
Todo: -
License of the code: MIT
Documentation PR: ~