ssh: check md5 fingerprints case insensitively (regression)

Revert the change from ce8d09483e but use the new function

Reported-by: Kamil Dudka
Bug: ce8d09483e (commitcomment-19666146)

lib/ssh.c

@@ -676,7 +676,7 @@ static CURLcode ssh_check_fingerprint(struct connectdata *conn)
    * against a known fingerprint, if available.
    */
   if(pubkey_md5 && strlen(pubkey_md5) == 32) {
-    if(!fingerprint || strcmp(md5buffer, pubkey_md5)) {
+    if(!fingerprint || !strcasecompare(md5buffer, pubkey_md5)) {
       if(fingerprint)
         failf(data,
             "Denied establishing ssh session: mismatch md5 fingerprint. "