Allocate the interface capabilities structure only if we succeed in
getting a pcap_t handle for it.
For remote devices, explicitly set caps->can_set_rfmon and
caps->data_link_types, to be a little bit more like what we do for local
devices.
Change-Id: I985c05f85f165fce4dfe0392569ec51ed1eeb91e
Reviewed-on: https://code.wireshark.org/review/20242
Reviewed-by: Guy Harris <guy@alum.mit.edu>