[DPP-63] GenProcess `call` interrupt results in chaos

[qnikst]

[Imported from JIRA. Reported by Tim Watson [Administrator] @hyperthunk) as DPP-63 on 2013-01-21 17:58:49]
I'm pretty sure this is a bug. If a callback decides to terminate mid-way through a gen-call it can create havoc for the client if they're monitoring the server. The bit that really worries me is this:

Mon Jan 21 17:34:13 UTC 2013 pid://127.0.GenServerTests: 0.too few bytes. Failed reading at byte position 651
:8080:0:6: terminating....
Mon Jan 21 17:34:13 UTC 2013 pid://127.0.0.1:8080:0:6: terminating counter when state = 10 because TerminateOther "Count > 10"
Mon Jan 21 17:34:13 UTC 2013 pid://127.0.0.1:8080:0:58: call: remote process died: DiedNormal
  exceed counter limits: [Failed]
ERROR: thread blocked indefinitely in an MVar operation

Now if we ignore the odd stdio interleaving, the key thing I'm concerned about is that the decoding of some message has blown up. Quite why this is happening, I'm not sure, though This might be to do with the use of terminate or (previously) fail in the async call worker process, but it's pretty awkward to debug.

[hyperthunk]

Was fixed before import