knownhosts: Fix invalid read of known_hosts token

Fixes invalid read introduced by commit 21962d.
Accessing tokens[4] for a known_hosts line of
three tokens led to randomly rejected host keys.

This commit completely removes the check because
the optional comments field may contain whitespace.

Signed-off-by: Tilo Eckert <tilo.eckert@flam.de>
(cherry picked from commit 45058285fc)

src/known_hosts.c

@@ -131,17 +131,13 @@ static char **ssh_get_knownhost_line(FILE **file, const char *filename,
       return NULL;
     }
 
-    if(!tokens[0] || !tokens[1] || !tokens[2]) {
+    if(tokens[0] == NULL || tokens[1] == NULL || tokens[2] == NULL) {
       /* it should have at least 3 tokens */
       tokens_free(tokens);
       continue;
     }
 
     *found_type = tokens[1];
-    if (tokens[3] || tokens[4]) {
-      tokens_free(tokens);
-      continue;
-    }
 
     return tokens;
   }