MSP-11253: Drop known protocol from Nexpose console address before save

All Nexpose console addresses use https, so we don't need to get the protocol from the user. We tack on the protocol automatically before attempting connection already, so if the user does include the protocol in the address when adding a console, an error results. This drops the protocol before saving.

# Verification Steps - within metasploit_data_models checkout dir
- [x] `bundle install`
- [x] `rake spec`
- [x] VERIFY no failures

# Verification Steps - within Pro
- [x] Update Gemfile#L53 to point to MDM checkout, e.g.: ```gem 'metasploit_data_models', :path => '/Users/YOOU/rapid7/mdm'```
- [x] bundle install
- [x] ```foreman start```
- [x] Administration -> Global Settings -> Nexpose Consoles
- [x] Add one, in the address field, include protocol, e.g. ```https://foo.nexpose.com```
- [x] VERIFY No validation errors, console saved and added successfully (hover over name to verify address)

# Post-merge Steps

Perform these steps prior to pushing to master or the build will be broke on master.

## Version
- [x] Edit `lib/metasploit_data_models/version.rb`
- [x] Remove `PRERELEASE` and its comment as `PRERELEASE` is not defined on master.

## Gem build
- [x] gem build *.gemspec
- [x] VERIFY the gem has no '.pre' version suffix.

## RSpec
- [x] `rake spec`
- [x] VERIFY version examples pass without failures

## Commit & Push
- [ ] `git commit -a`
- [ ] `git push origin master`


# Release

Complete these steps on DESTINATION

## Version

### Compatible changes

If the change are compatible with the previous branch's API, then increment [`PATCH`](lib/metasploit_data_models/version.rb).

### Incompatible changes

If your changes are incompatible with the previous branch's API, then increment
[`MINOR`](lib/metasploit_data_models/version.rb) and reset [`PATCH`](lib/metasploit_data_models/version.rb) to `0`.

- [ ] Following the rules for [semantic versioning 2.0](http://semver.org/spec/v2.0.0.html), update
[`MINOR`](lib/metasploit_data_models/version.rb) and [`PATCH`](lib/metasploit_data_models/version.rb) and commit the changes.

## JRuby
- [ ] `rvm use jruby@metasploit_data_models`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install`
- [ ] `rake release`

## MRI Ruby
- [ ] `rvm use ruby-1.9.3@metasploit_data_models`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install`
- [ ] `rake release`