Fix reversion introduced in version 6.20180316 that caused git-annex to
stop processing files when unable to contact a ssh remote.
The bug was not in any of the changed lines, but this one in inAnnex:
P2PHelper.checkpresent (Ssh.runProto rmt connpool (cantCheck rmt) fallback) key
cantCheck throws an exception, but that parameter to runProto expects a
value, which it returns. So, inAnnex is returning a Bool containing an
exception. This defeats the usual checks for checkPresent throwing an
exception, crashing git-annex.
Fixed by making runProto take an `Annex a` instead of an `a`, so
passing cantCheck to it doesn't nest exceptions.
This commit was sponsored by andrea rota.
9f3a346f25