fix: what bandit and the remaining lint rules found

- Long shell command lines are split into adjacent string literals.
- get_os_users: a first loop over /etc/group filled a map nobody read;
  it is gone, the output is unchanged.
- The five except Exception: pass now log at debug level (B110), so a
  swallowed failure leaves a trace.
- nosec for the staging path on the device (B108) and the sudo hint
  message (B105); both are false positives.
- tests: raise ... from exc, unused loop variable.

tests/test_ssh_host_key.py

@@ -78,7 +78,7 @@ def test_a_changed_key_is_refused():
         try:
             raise paramiko.BadHostKeyException("10.0.0.8", SERVER_KEY, OTHER_KEY)
         except paramiko.SSHException as exc:  # what netmiko does with it
-            raise NetmikoTimeoutException(f"A paramiko SSHException occurred: {exc}")
+            raise NetmikoTimeoutException(f"A paramiko SSHException occurred: {exc}") from exc
 
     driver = _driver(seen, SshHostKey.of(OTHER_KEY))
     with patch("napalm_linux.linux.ConnectHandler", side_effect=refuse):