Fixes #4897: Move r32686 to v1.8 branch (Wrap MCA params)

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r32686 [[BR]]
Since we've run into the situation where someone puts a script wrapper around a launcher such as srun, we need to always protect MCA cmd line params with quotes. This means we also need to protect the backend from quotes coming into the system as part of a value, or else the parser gets confused.

So add a new function for wrapping MCA arguments, and tell the backend parser to ignore/remove leading/trailing quotes.

cmr=v1.8.3:reviewer=jsquyres


r32719 [[BR]]
Check for multiple declarations of a given MCA param and error out if detected as that can create an ambiguous definition of the param value.

Refs #4897


r32726 [[BR]]
plm_rsh_module.c: output to the framework output

Trivial fix from r32686: don't output to stream 0, but rather to
orte_plm_base_framework.framework_output (this is the way it was
before r32686).  In reality, this is going to end up being stream 0,
anyway, but we might as well be pedantically correct...

Refs #4897.

r32731 [[BR]]
Not sure how we could get to this point without having already detected the error, but just to be safe - check for end-of-array and return if error.

Refs #4897