tools/libxl: Do not use remus teardown paths for non-remus guests

tools/libxl: Do not use remus teardown paths for non-remus guests

It causes a suspend failure to emit

  libxl: error: libxl_dom.c:2035:remus_teardown_done: Remus: failed to
  teardown device for guest with domid 17, rc -3

for all domains, including those not using remus at all.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>