[Bruce Schuchardt]

I had a test run where a member was suspected by FD_SOCK, but replied to an
ARE_YOU_DEAD message. The process was then immediately killed by the test
but was never suspected again.

FD_SOCK.run() removes suspected members from pingable_mbrs so they won't be
ping targets. When a member is unsuspected, it needs to be put back in
pingable_mbrs in the correct place and the pinger thread needs to be started
or interrupted. Otherwise no-one will be watching the unsuspected member
until the next view change.