cleanup dependency in tox.ini
cleanup dependency in tox.ini

This removes unnecessary dependency from deps list because
all tests except keystone don't require keystone package.

Change-Id: I67cb4b74782e565082c1fc1ebab6f5fe6204a38b

swiftstack/swift3-stackforge,stackforge/swift3,tumf/swift3,stackforge/swift3,KoreaCloudObjectStorage/swift3,swiftstack/swift3-stackforge,tumf/swift3,KoreaCloudObjectStorage/swift3