Adding/creating new lua APIs: "ts.server_request.set_url_host", "ts.server_request.get_url_host", "ts.server_request.set_url_scheme", and "ts.server_request.get_url_scheme "

Create new lua APIs "ts.server_request.set_url_host", "ts.server_request.get_url_host", "ts.server_request.set_url_scheme", and "ts.server_request.get_url_scheme " to Set/Get scheme and host name in the server request to next tier.

These APIs are useful to remove scheme and host name in the request to parent, which help to have a parent remap.config entry similar to child cache. This makes provisioning more meaningful and easy at both parent and child.

With this fix, the GET request to parent will change..

from:

+++++++++ Proxy's Request +++++++++
– State Machine Id: 5593
GET http://origin.com/dir1/a.txt HTTP/1.1^M
User-Agent: curl/7.29.0^M
Host: abc.com^M
Accept: /^M
Client-ip: 135.xx.xx.xx^M
X-Forwarded-For: 135.xx.xx.xx^M

To:
+++++++++ Proxy's Request +++++++++
– State Machine Id: 5593
GET /dir1/a.txt HTTP/1.1^M
User-Agent: curl/7.29.0^M
Host: abc.com^M
Accept: /^M
Client-ip: 135.xx.xx.xx^M
X-Forwarded-For: 135.xx.xx.xx^M

This will enable to have parent and child's remap.config entries as below:

map http://abc.com http://origin.com @plugin=tslua.so @pparam=/opt/trafficserver/etc/trafficserver/lua/test.lua