gitignore etc/keystone/

this is the default directory used by pki_setup and ssl_setup if running
with a keystone.conf alongside keystone.conf.sample for development...
for example:

$ tree etc/keystone/
etc/keystone/
└── ssl
    ├── certs
    │   ├── 01.pem
    │   ├── ca.pem
    │   ├── index.txt
    │   ├── index.txt.attr
    │   ├── index.txt.old
    │   ├── openssl.conf
    │   ├── req.pem
    │   ├── serial
    │   ├── serial.old
    │   └── signing_cert.pem
    └── private
        ├── cakey.pem
        └── signing_key.pem

3 directories, 12 files

Change-Id: I6264805dc91bc165e930708c2781074aa0b29070
Merge "gitignore etc/keystone/"