mon_thrash: use _ instead of - consistently

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 389f65e7a6e4d68694d6ac0f63e61c83aaa2a40b)
mon_thrash: fix more naming

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 9b22d388835b8074fdcfa51deb019b666e3b186f)
mon_thrash: optionally scrub after each iteration (default true)

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 121b1b9f385831154b0eb2a037a3d7c4ccfcfdd4)
mon_thrash: tolerate missing 'scrub' command

Signed-off-by: Sage Weil <sage@inktank.com>
daemon-helper: send arbitrary signals via stdin

Each byte written to stdin will be interpreted as a signal.

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit fdebf40f342d368efee7d9bdf8d0cbf1d489f097)
mon_thrasher: add pause/unpause of mons to thrashing

This adds an additional element of laggyness to the cluster which should
cause mons to call new elections.

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit a0457492ccaaf1cc3342f5284459402563c6224a)