Add missing mutex lock/unlocks when accessing conntab

(problem introduced in parent commit).

sshfs.c

@@ -2499,11 +2499,13 @@ static int sshfs_rename(const char *from, const char *to, unsigned int flags)
  err = -EXDEV;
 
  if (!err && sshfs.max_conns > 1) {
+ pthread_mutex_lock(&sshfs.lock);
  void *conn = g_hash_table_lookup(sshfs.conntab, from);
  if (conn != NULL) {
  g_hash_table_replace(sshfs.conntab, g_strdup(to), conn);
  g_hash_table_remove(sshfs.conntab, from);
  }
+ pthread_mutex_unlock(&sshfs.lock);
  }
 
  return err;
@@ -2849,6 +2851,7 @@ static int sshfs_release(const char *path, struct fuse_file_info *fi)
  buf_free(handle);
  chunk_put_locked(sf->readahead);
  if (sshfs.max_conns > 1) {
+ pthread_mutex_lock(&sshfs.lock);
  sf->conn->file_count--;
  if(!sf->conn->file_count)
  g_hash_table_remove(sshfs.conntab, path);