Fix the clang 12 warnings with multi-line strings in string arrays

Fix the clang 12 warnings with multi-line strings in string arrays

The clang 12 has a new warning that warns when using multi-line strings
in the string arrays, f.e.:

    { "aa",
      "b"
      "b",
      "cc" }

would generate warning like this:

    private_test.c:162:7: error: suspicious concatenation of string literals in an array initialization; did you mean to separate the elements with a comma? [-Werror,-Wstring-concatenation]
                                      "33333/RSASHA1" };
                                      ^
    private_test.c:161:7: note: place parentheses around the string literal to silence warning
                                      "Done removing signatures for key "
                                      ^
    private_test.c:197:7: error: suspicious concatenation of string literals in an array initialization; did you mean to separate the elements with a comma? [-Werror,-Wstring-concatenation]
                                      "NSEC chain",
                                      ^
    private_test.c:196:7: note: place parentheses around the string literal to silence warning
                                      "Removing NSEC3 chain 1 0 30 DEAF / creating "
                                      ^
    2 errors generated.

(cherry picked from commit 7b07f22969149ceb24ad9491696fabb66c333524)