man: moved virsh command cpu-models
    
    The description of the virsh command 'cpu-models' was written in the
    wrong context (i.e. beside the domain states).
    This patch moves the command description just to the cpu related
    commands like 'cpu-baseline' and 'cpu-compare'.
    
    Signed-off-by: Daniel Hansel <daniel.hansel@linux.vnet.ibm.com>