Warning from clang in test_dir.c

  CC       src/test/test-test_dir.o
src/test/test_dir.c:2139:9: error: suspicious concatenation of string literals in an array initialization; did you mean to separate the elements with a comma? [-Werror,-Wstring-concatenation]
        "unmeasured=0\n",
        ^
src/test/test_dir.c:2138:5: note: place parentheses around the string literal to silence warning
    "node_id=$557365204145532d32353620696e73746561642e bw=1024 vote=0 "
    ^
1 error generated.