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:

- [x] Download Axis2: http://axis.apache.org/axis2/java/core/download.cgi
- [x] Install it: http://axis.apache.org/axis2/java/core/docs/installationguide.html#standalone1
- [x] Make sure the login part is working properly: /axis2/axis2-admin/login
- [x] Start ```msfconsole```
- [x] ```use auxiliary/scanner/http/axis_login```
- [x] ```set rhosts [IP]```
- [x] ```set username [valid user]```
- [x] ```set password [valid pass]```
- [x] ```set stop_on_success true```, but you don't have to if you don't want to.
- [x] ```run```.
- [x] You should not see a "The Axis2 login page does not exist at xxx" error.
After reviewing code.... I'm not sure of understanding this request. If the purpose of this request is to validate which there is really an axis2 login page, just rescuing doesn't look like enough. Could you use this PR to validate  which really there is an axis2 login page on the url :? Thanks!