libctdb: test infrastructure

libctdb: test infrastructure

This introduces 'ctdb-test', a program for testing libctdb.  It takes
commands on standard input (with reduced functionality) or an input file.

It still needs some cleaning up, but you can uncover a bug in libctdb
today simply by running a simple attachdb test:

	$ ctdb-test tests/attachdb1.txt

It will print out a crash, and the path of successful and failed
operations which lead to it:

	...
	Child signalled 11 on failure path: [malloc]:1:S[socket]:1:S[connect]:1:S[malloc]:1:S[malloc]:1:S[malloc]:1:S[malloc]:4:S[malloc]:4:F

Feed that failure path into ctdb-test using --failpath (under a debugger):

	gdb --args ctdb-test tests/attachdb1.txt --failpath=[malloc]:1:S[socket]:1:S[connect]:1:S[malloc]:1:S[malloc]:1:S[malloc]:1:S[malloc]:4:S[malloc]:4:F

And you hit the exact error.

It is based on the fork-to-fail model of nfsim.  The relevant parts are
from page 154 of the proceedings of 2005 Ottawa Linux Symposium Volume II:
	http://www.linuxsymposium.org/2005/linuxsymposium_procv2.pdf

Or our presentation of same (from slide 21):
	http://ozlabs.org/~jk/projects/nfsim/nfsim.sxi

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(This used to be ctdb commit b4aab4199a57898877b6545a54f212087ed4b35a)