Make vncterm optional
Make vncterm optional

Already if vncterm fails then it's treated as a soft failure. Some
people prefer to use raw xenconsole anyway.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@citrix.com>

djs55/xenopsd,thomassa/xenopsd,koushikcgit/xenopsd,thomassa/xenopsd,johnelse/xenopsd,johnelse/xenopsd,djs55/xenopsd,thomassa/xenopsd,cheng--zhang/xenopsd,koushikcgit/xenopsd,euanh/xenopsd,johnelse/xenopsd,euanh/xenopsd,cheng--zhang/xenopsd,euanh/xenopsd,cheng--zhang/xenopsd,koushikcgit/xenopsd,djs55/xenopsd