mod_proxy_http: common function for stream_reqbody_{cl,chunked}()

Since stream_reqbody_cl() and stream_reqbody_chunked}() now have the same
structure, join them into a single stream_reqbody() function which is passed
the rb_method to handle only CL vs chunked cases differently.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1853953 13f79535-47bb-0310-9956-ffa450edef68