Having an executor within clusterctl.client package creates
potential import cycling. This patch moves it to a separate
package which can be used to conveniently store all the executors
at one place.
Change-Id: Ib0a6072a393e68885d9ef911aa2894a0de055668
Signed-off-by: Ruslan Aliev <raliev@mirantis.com>
Relates-To: #374
71dc1d4703