Fix #3974 - Validate and normalize URI for axis_login

This fixes https://github.com/rapid7/metasploit-framework/issues/3974

It will validate and normalize the URI before using it in a request, based on the following wiki:
https://github.com/rapid7/metasploit-framework/wiki/How-to-Send-an-HTTP-Request-Using-HTTPClient#uri-parsing

## Verification:

- [ ] Download Axis2: http://axis.apache.org/axis2/java/core/download.cgi
- [ ] Install it: http://axis.apache.org/axis2/java/core/docs/installationguide.html#standalone1
- [ ] Make sure the login part is working properly: /axis2/axis2-admin/login
- [ ] Start ```msfconsole```
- [ ] ```use auxiliary/scanner/http/axis_login```
- [ ] ```set rhosts [IP]```
- [ ] ```set username [valid user]```
- [ ] ```set password [valid pass]```
- [ ] ```set stop_on_success true```, but you don't have to if you don't want to.
- [ ] ```run```.
- [ ] A successful login should indicate the URI parsed correctly