Fix check for is_virtual fact
Fix check for is_virtual fact

Some versions of facter, such as 2.0.1, return a string for fact
is_virtual. Commit 1e7c1621039a735c69a7f28fc68d21e73562d544 exposed
this as a bug, and it is actually fixed in later facter versions.
To stay compatible with earlier versions, use str2bool to convert
strings to boolean when handling is_virtual.

Change-Id: I516f3290e82729ae5d747a3921f382693cc3e407

xbezdick/packstack,fr34k8/packstack,mahak/packstack,stackforge/packstack,imcsk8/packstack,openstack/packstack,openstack/packstack,mahak/packstack,xbezdick/packstack,stackforge/packstack,openstack/packstack,imcsk8/packstack,fr34k8/packstack,stackforge/packstack,fr34k8/packstack,imcsk8/packstack,mahak/packstack,xbezdick/packstack