simpletrace: fix timestamp argument type

simpletrace: fix timestamp argument type

The timestamp argument to a trace event method is documented as follows:

  The method can also take a timestamp argument before the trace event
  arguments:

    def runstate_set(self, timestamp, new_state):
        ...

  Timestamps have the uint64_t type and are in nanoseconds.

In reality methods with a timestamp argument actually receive a tuple
like (123456789,) as the timestamp argument.  This is due to a bug in
simpletrace.py.

This patch unpacks the tuple so that methods receive the correct
timestamp argument type.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180222163901.14095-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>