sky: Initialize energest as early as possible

If energest is initialized too late, the radio is not accounted
until the first switch. This is a problem when the radio is always
listening.
Support running multiple random seeds in case one fails
Only fail on real fails
Merge pull request #810 from cmorty/pull/sky_energest

sky: Initialize energest as early as possible / make regression testing more tolerant
packetbuf: Added function "packetbuf_holds_broadcast()" for checking whether the current packet is a
broadcast
packetbuf: Use packetbuf_holds_broadcast() all-over
framer-802154: Create without frame802154.c
framer-802154: Parse without frame802154.c
nullrdc: Removed dependency on frame802154.c