Add the SASL protocol for memcached, to improve the security of authority.
SASL(Simple Authentication and Security Layer): is a memchanism used to
extend the verification ability of C/S mode. SASL is only the
authentication process, which integrates the application layer and the
system authentication mechanism. However, the current memcached hasn't
any authenticaction mechanism to protect the user's data cached in
memcached server.
Depends-On: 7828bed0febabfa11a0a8f6960f4c7cc8acec841
Implements: blueprint enable-sasl-protocol
Change-Id: I40b9f4eac518f34a3dfb710b5c4ab3a76da7c00c
d229d3edb7