Mask passwords in exceptions and error messages

When a ProcessExecutionError is thrown by processutils.ssh_execute(),
the exception may contain information such as password. Upstream
applications that just log the message (as several appear to do)
could inadvertently expose these passwords to a user with read access to
the log files. It is therefore considered prudent to invoke
strutils.mask_password() on the command, stdout and stderr in the
exception. A test case has been added (to oslo-incubator) in order to 
ensure that all three are properly masked.

An earlier commit (853d8f9897f8563851441108a9be26b10908c076) failed
to address ssh_execute(). This change set addresses ssh_execute.

OSSA is aware of this change request.

Change-Id: Ie0caf32469126dd9feb44867adf27acb6e383958
Closes-Bug: #1377981
Update rpc version aliases for juno

Update all of the rpc client API classes to include a version alias
for the latest version implemented in Juno.  This alias is needed when
doing rolling upgrades from Juno to Kilo.  With this in place, you can
ensure all services only send messages that both Juno and Kilo will
understand.

Closes-bug: #1378786
Change-Id: Ia81538130bf8530b70b5f55c7a3d565903ff54b4
(cherry picked from commit f98d725103c53e767a1cddb0b7e2c3822309db17)
Merge "Mask passwords in exceptions and error messages" into proposed/juno
Merge "Update rpc version aliases for juno" into proposed/juno