Fix swift functional test "test_create_store"

Fix "test_create_store" when a real swift store is used
via the GLANCE_TEST_SWIFT_CONF environment variable.

Fixes bug: 1292170
Change-Id: I500c1d0caee30449146b732b1105b20b7a0d5d05
Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>