knucleotide version where each write_count runs in parallel

git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23656 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Forgot to do a membership check on the associative domain

git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23657 3a8e244f-b0f2-452b-bcba-4c88e055c3ca