1. Changed drivers to prevent using global CONF but access it from
client by interface.
2. Corrected swift driver to involve options from swift driver utils,
allow glance_store exports and registers them for client.
3. Added missing test cases for the functions of swift driver util.
Change-Id: I8fac6800efde202e29179791ea05c4814ec58435
Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>