Handle RHEL5 under Xen PVM

Handle RHEL5 under Xen PVM.  RHEL5 under Xen needs a special entry in inittab
for the XenCenter console.  An agetty is hung on /dev/xvc0, which is provided
by the XenU Kernel and connects to a xterm in a VNC session on the Xen server
hosting the VM, which is then connected to by the XenCenter management GUI
so that the system console appears on the Console tab for a given VM.
Use one template for EL5

Places conditional logic in template in order to not duplicate the file.
Add spec tests for Xen on EL5
Merge pull request #64 from ghoneycutt/support_rhel5_xen

Support EL5 with Xen