Changes

ctf.core: Change seeking algorithm

The current seeking algorithm relies on using the packet end time to
seek to the correct event with a timestamp however this time is often
not available in the packet header which makes the current algorithm go
through every event in the trace individually. This patches solves that
by going through every packet until the event at the start of the packet
has a larger timestamp, then it goes backward until it finds a packet
with every event smaller and returns the first bigger event previously
found.

Signed-off-by: Arnaud Fiorini <fiorini.arnaud@gmail.com>
Change-Id: I5cce9cd2864e400ec939253e75f690286fd90b6e