Fix the 'ssh failed to start error' on every chef run.

[macmaster]

This change pulls out the first commit of #1271 and just applies a simple diff to fix the error.
The default service provider now works fine for ssh on ubuntu 14.04, so we can use it instead of a manual execution resource.

Tested under the following scenarios:

• ssh is disabled, not yet running.
• ssh is disabled, already running.
• ssh is enabled, not yet running.
• ssh is enabled, already running.

Tested using the following methods:
Disable the service with:

$ sudo chef-shell
chef (12.19.36)> recipe_mode
chef:recipe (12.19.36)> service 'ssh' do
chef:recipe > action :disable
chef:recipe ?> end
chef:recipe (12.19.36)> run_chef

Modify and check the status of ssh with:

$ sudo service ssh stop
$ sudo service ssh status
$ sudo service ssh start

Run this recipe with chef:

$ sudo chef-client -o 'bcpc::ssh'

[cbaenziger]

The specifics of the tests are quite important; this code runs under at least a few different scenarios:
• SSH service not enabled
• SSH service running but disabled
• SSH service enabled and running
• SSH service not running seems unlikely since we ssh in

Please confirm if you've tried these three (or anyone comment if you can think of more)

[macmaster]

The specifics of the tests are quite important; this code runs under at least a few different scenarios:
• SSH service not enabled
• SSH service running but disabled
• SSH service enabled and running
• SSH service not running seems unlikely since we ssh in

Please confirm if you've tried these three (or anyone comment if you can think of more)

Now tested under the following circumstances:

• ssh is disabled, not yet running.
• ssh is disabled, already running.
• ssh is enabled, not yet running.
• ssh is enabled, already running.

[cbaenziger]

Thanks for the verification!