Added api client
moved ClearReboot
Added test for ClearReboot
Merge pull request #744 from gabriel-samfira/reboot-apiclient

Added reboot api client

This is the third pull request for the reboot implementation. Please note that this is still a Work in Progress and a followup commit will be done for cleanup.

This PR depends on:

https://github.com/juju/juju/pull/707
https://github.com/juju/juju/pull/728