Release process failed to detect that header file was not installed.

9.15.8 failed to install isc/netmgr.h

My sanity check script had this post install check and a similar one for a install from a out-of-tree build to detect .h files that where not installed.

  for f in `find $i/lib -name \*.h | grep -v win32 | grep -v include/tests/t_api.h | grep -v include/isc/ipv6.h | sed -n 's;.*include/;'"${i}-test-install"'/usr/local/include/;p'`
  do
        case $i in
        bind-9.[89]*)
                expr "$f" : '^.*/include/irs/.*\.h$' > /dev/null && continue
                ;;
        esac
        test -f $f || echo missing $f
  done