Optionally allow ec2token config to come from .conf

Just like keystoneclient.middleware.auth_token
first checks paste.ini file then .conf file when fetching
a config value

Change-Id: I9db9744d0ab12fcf486de9a9d3f8e870a4ff66de
Move ec2token defaults from paste.ini to .conf

paste.ini files can now be considered not user-editable
(in normal circumstances)

Change-Id: Ia2a6d784ed2fad009de9e77717e6e0dc00c5e2f4
Merge "Optionally allow ec2token config to come from .conf"
Merge "Move ec2token defaults from paste.ini to .conf"