When a caller passes an os_options dict to the Connection class
constructor, the constructor may modify the os_options dict,
which can surprise the caller if they re-use the os_options
dict. Specifically the os_options tenant_name and object_storage_url
may be modified, and the changed values would then leak through to a
subsequent Connection constructed using the same os_options dict.
This fix simply constructs a new dict from the supplied os_options.
The patch also adds a test that covers this and also verifies that
a preauth_url passed as a keyword arg to Connection() will take
precedence over any object_storage_url in an os_options parameter.
Closes-Bug: 1488070
Change-Id: Ic6b5cf3ac68c505de155619f2610be9529e15432
4b310083df