Fix UsedLimitsController's authorizer to soft

Fix UsedLimitsController's authorizer to soft

The rule "limits_extension:used_limits" is used by
"UsedLimitsController" which is a controller extension and it extends
"limits" api. Most of controller extensions authorize user's context
by applying the function "extensions.soft_extension_authorizer()",
but "UsedLimitsController" applies "extensions.extension_authorizer"
and this may cause 403 Forbidden error.

In this patch, I changed UsedLimitsController's authorizer to
"soft_extension_authorizer".

APIImpact

Co-Authored-By: ZhuChunzhan <zhucz@cn.fujitsu.com>
Change-Id: I8a4163ca89236b35c2c6ba10bcd98f8c42ef9089
Closes-Bug: #1497868