prevent sending ContactRequest with no vCard

missing edit in d57d2748 make the next bug still present :
the vcard sent was obtained trough a Person object returned by
contact() from a ContactMethod. But this Person may be never set.

fix : now we use the profile to get the vcard to send within the
ContactRequest.

Change-Id: I150715b45bf564fa7e0fb3fae5b186375dfe0ec1
Reviewed-by: Stepan Salenikovich <stepan.salenikovich@savoirfairelinux.com>