webdav: add a litmus test server.
webdav: add a litmus test server.

Change-Id: I1e109180673cf3caff4413d12b77422bb072ac50
Reviewed-on: https://go-review.googlesource.com/2950
Reviewed-by: Dave Cheney <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@cheney.net>
Reviewed-by: Nick Cooper <d8c7b1721c483bd3ff883e3abbcd3cf7133480b3@google.com>

veliamsli/net,subuk/net,foreversmart/net,mckinney-subgraph/net,golang/net,cmars/tools,albertjin/golang-net,cesanta/goxnet,flowlo/go-net,yangxianjun/net,cmars/tools,yangxianjun/net,subuk/net,dafyddcrosby/net,kiip/net,mckinney-subgraph/net,DramaFever/golang.org-x-net,cmars/tools,cesanta/goxnet,zabawaba99/net,cmars/tools,zabawaba99/net,gomini/net,raboof/net,kiip/net,gomini/net,chenzlabs/net,muzining/net,w4ngyi/net,chenzlabs/net,muzining/net,DramaFever/golang.org-x-net,w4ngyi/net,albertjin/golang-net,raboof/net,foreversmart/net,flowlo/go-net,veliamsli/net,dafyddcrosby/net