stop using timerfd and signalfd

Current DynamoRIO doesn't support timerfd and signalfd, so this patch
let sheepdog stop using them. This is a temporal, adhoc stuff.
tests: add a DynamoRIO client for testing the jounaling mechanism

This patch adds a DynamoRIO (often called DR) client for testing the
jounaling mechanism. Because of its nature, the recoverying path is
the most important and hard to test part of the journaling
mechanism. They need to be tested well.

But testing targetted recovery paths with traditional tests/ stuff is
hard because:
1. killing sheeps with kill commands doesn't take into account the
   internal state
2. inserting exit()s into sheep manually is a painful work

So this patch implements a fault injection mechanism with DR. DR
provides rich functionalities of transparent dynamic
instrumentation. One of the functionalities makes inserting function
calls before and after system calls possible. With this mechanism, the
fault injection mechanism lets sheep exit at suitable timings for
testing recovery paths of the journaling.

How to use:
0. preparation
   $ cd
   $ svn checkout http://dynamorio.googlecode.com/svn/trunk/ dynamorio
   $ cd dynamorio
   $ mkdir build
   $ cd build
   $ cmake ..
   $ make

(This patch assumes the source code of DR is store in $HOME/dynamorio,
and the build is done in $HOME/dynamorio/build)

1. build the DR client
   $ cd tests/dr_clients/journal_fi/
   $ cmake .
   $ make

2. run tests with preset scenarios
   $ ./01.sh 	  # for testing recovery of object store
   $ ./02.sh 	  # for testing recovery of epoch
   $ ./03.sh 	  # for testing recovery of config

The fault injection implemented with this patch is so slack and not
capable for exhaustive testing. It is clear that we need unified,
programmable fault injection mechanism for testing distributed
systems. This is only a supoprted care. But I believe it is useful.

With this patch, I tested these recovery paths and checked they work
well.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>