Refactor: cts,python: Clean up uses of the call function.

• The blocking and delegate arguments are never passed, so remove them. blocking wasn't even referenced anywhere besides in the parameters.

• synchronous is a boolean, so treat it like such.

• Replace silent= with verbose=0/1/2 to help alleviate some of the output changes caused by this patch. Because we were keying on the stdin= parameter to both change the return type and control how much gets printed, there's not really a good way to preserve output with just the silent= parameter - something always gets added or left out regardless.

• Always return the same type - a tuple of (rc, output). It's up to the callers to handle extracting the data they want from this tuple.

• If callers don't do anything with one element of the tuple, assign it to _. If callers don't do anything with the return value at all, just don't assign it to anything.

• Remove unnecessary arguments from calls.

• Do a better job of handling the possibility that output is empty in various places. There's likely a whole lot more of this to do.

• Add a comment to the function.