fix truncation warnings for strncpy(3)

Problem: Modern compilers warn of possible truncation in calls to
strncpy(3) in the pdsh codebase.

Fix the warnings in hostlist.c and wcoll.c by reducing the size to
copy by one character.

src/common/hostlist.c

@@ -1512,7 +1512,7 @@ _hostlist_create_bracketed(const char *hostlist, char *sep, char *r_op)
     }
 
     while ((tok = _next_tok(sep, &str)) != NULL) {
-        strncpy(cur_tok, tok, 1024);
+        strncpy(cur_tok, tok, 1023);
 
         if ((p = strchr(tok, '[')) != NULL) {
             char *q, *prefix = tok;

src/pdsh/wcoll.c

@@ -187,10 +187,10 @@ static char * wcoll_ctx_resolve_path (struct wcoll_ctx *ctx,
         const char *file, char *buf, int len)
 {
     if (file[0] == '/')
-        strncpy (buf, file, len);
+        strncpy (buf, file, len - 1);
     else if ( file[0] == '.'
             && (file[1] == '/' || (file[1] == '.' && file[2] == '/')))
-       strncpy (buf, file, len);
+       strncpy (buf, file, len - 1);
     else {
         if (wcoll_ctx_path_lookup (ctx, file, buf, len) < 0)
             return NULL;