Use thread when typing boot sequence

In some cases typing the delay in finishing the console_type method is longer than the boot process of the virtual machine. In these cases the kickstart server will only be started after the VM searches for it, which usually results in an error.

Putting the console_type method into a thread solves this problem,  as it ensures that the kickstart server starts to wait for connections before the typing is finished.

The issue has been observed with the KVM provider, but may also occur for other providers. The fix will work for all providers and does not change the current behavior.
Merge pull request #488 from ffeldhaus/build-thread

Use thread when typing boot sequence