Add TID field to some block_* events

Most of the block events have the "comm" field, but we have no way to
match a block event to a certain thread which makes performing
accurate per-thread analyses difficult. Add the TID field to the events
that already export current->comm.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>