Make reseller admin role configurable

This commit makes the reseller admin role configurable. Previously the
swift tests which used the reseller admin role had hardcoded the role
to be the default ResellerAdmin. However the role is configurable, so
this commit adds a new config option which can be used to set the role
to something besides the default.

Change-Id: I3296a343480d4a0e0e4099863eb8869ffb0f83c3
Merge "Make reseller admin role configurable"