put retry blocks around record creations

VERIFICATION STEPS

- [ ] pull down this branch
- [ ] point pro gemfile to local path
- [ ] start pro
- [ ] new project
- [ ] 10.20.39.0/24as the network range
- [ ] select all hosts
- [ ] run psexec with msfadmin:msfadmin
- [ ] VERIFY no activeRecord errors


# Release

Complete these steps on DESTINATION

## `VERSION`

### Compatible changes

If your change are compatible with the previous branch's API, then increment [`PATCH`](lib/metasploit/credential/version.rb).

### Incompatible changes

If your changes are incompatible with the previous branch's API, then increment [`MINOR`](lib/metasploit/credential/version.rb) and reset [`PATCH`](lib/metasploit/credential/version.rb) to `0`.

- [ ] Following the rules for [semantic versioning 2.0](http://semver.org/spec/v2.0.0.html), update [`MINOR`](lib/metasploit/credential/version.rb) and [`PATCH`](lib/metasploit/credential/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`