Update the sqlcmd readme, many small fixes...
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Merge pull request #337 from VoltDB/notest-eng-4187

Update the sqlcmd readme, many small fixes...
ENG-4191: Make the masters needed for restart thread-safe.
ENG-4191: Ensure that we always sandwich a restart
CompleteTransactionMessage in between attempts to restart a
transaction.  Interruption of the MpPromoteAlgo could lead to a path
where we didn't do this.
Add CompleteTransactionMessage reception to the Iv2Trace logging.
ENG-4120: Part 2.  Demote log message for unregistered mailbox.  Turns
out it's non-trivial to make the startup code which is generating
these not send the messages to the not-yet-existing ClientInterfaces.
These will still end up in the logfile and any situation which causes
them will be fraught with plenty of other WARNs.
ENG-4185:  Increase the MP deadlock notification timeout to 5
minutes.
ENG-4183: Remove the WARN message when running with IV2 enabled.
Slightly modify the WARN message presented if legacy mode is chosen.
ENG-2353.  Apply Ariel's patch to get crash stack trace.
ENG-4204 Tolerate missing procedures

UpdateApplicationCatalog can remove a procedure from a site
after the clientinterface valided the procedure's presence
but before the site executes the procedure. Tolerate this.

Generate an UNEXPECTED FAILURE response and log the error
with the likely explanation.
ENG-4204 (Legacy) Don't hoarde catalogs in stats.

Flush PROCEDURE selector statsSources on catalog update or
the selector keeps a reference to the old catalog.
Merge remote-tracking branch 'origin/master' into ENG-4195-oldcatalogs