exit on fail: doesn't work
Revert "exit on fail: doesn't work"

This reverts commit eac930e22ddb1354eaa6ebda44eac4935b677405.
"failed" state in consensus_fsm
do nothing in handle_sync_event and handle_info when in failed state
failure_timeout -> restart
start_failures, stop_failures
small fixes
disallow multiple start_failures calls
report time-to-commit (TTC)
populate started field on read request
rafter_ttc_log.erl: initial commit
start rafter_ttc_log
use rafter_ttc_log instead of printing to stdout
"failure_timeout" -> "correlated_failure_timeout"
rewrote failure simulation
individual_fail -> repeated_fail
"ok"
correlated -> oneoff
log failure time
handle restart message