uipcp: enrollment: improve normal_ipcp_enroll()
uipcp: enrollment: improve normal_ipcp_enroll()

With this patch, if a client asks for a certain enrollment while
this is in progress, or after it has completed, this function will
behave correctly, not allocating another flow and waiting for the
enrollment procedure to complete (or abort).

autrimpo/rlite,vmaffione/rlite,vmaffione/rlite,autrimpo/rlite,vmaffione/rlite,autrimpo/rlite,autrimpo/rlite,vmaffione/rlite