[flang][runtime] Fix bug with NAMELIST in child input (#159173)
Don't let "hitSlash_" flag in child input propagate back to the parent
input statement's state when the child input was NAMELIST and the
NAMELIST input has properly consumed the terminal '/' character. (It can
get set if NAMELIST item input ran into it.) The current failure to
reset that flag is causing list-directed parent input to stop early.
Fixes https://github.com/llvm/llvm-project/issues/159127.