RkPropagator : Fix cppcheck warning

This is actually a bugfix

• Ping @ssnyder whose cppcheck found this one (!62519 (closed) was an attempt but has the "wrong" return if the 1st has succeeded and we did not need the 2nd step)

• When this bug was introduced last month , it passed FT0 tests ...

• Let me ping @jmaurer @strichte . I would hope it passes also today but maybe things changed ...

• Strictly speaking (although we might see no diff) the bug should have broken FT0 and so the fix might also do and therefore is "FT0 changing"

The original/fixed version will do

• one step.
• Then if this succeeds and further conditions are met will try a second and return that,
• otherwise the result of the 1st step is returned.