fix runtime arg exec

[iignatevich]

No description provided.

[davidferlay]

Somehow it seems to break actions using ssh tunnel:

• With fix:

➜ plx platform:data-bus list --cluster dev --keyring-passphrase-file /tmp/kp
Could not open a connection to your authentication agent.
2025/06/11 15:15:27 exit status 2
  ERROR   action "platform:data-bus" finished with exit code 1

• Without fix:

➜ pl platform:data-bus list --cluster dev --keyring-passphrase-file /tmp/kp 
SSH_AUTH_SOCK=/tmp/socket; export SSH_AUTH_SOCK;
SSH_AGENT_PID=8; export SSH_AGENT_PID;
echo Agent pid 8;
Enter passphrase for /tmp/id_rsa: Identity added: /tmp/id_rsa (/tmp/id_rsa)
# 51.159.2.47:1337 SSH-2.0-OpenSSH_9.7
# 51.159.2.47:1337 SSH-2.0-OpenSSH_9.7
# 51.159.2.47:1337 SSH-2.0-OpenSSH_9.7
# 51.159.2.47:1337 SSH-2.0-OpenSSH_9.7
# 51.159.2.47:1337 SSH-2.0-OpenSSH_9.7
NAME                                                                                                                          PARTITIONS  REPLICAS
.metric                                                                                                                       5           1
fluent-bit                                                                                                                    5           1

All other actions looks ok

[lexbritvin]

I don't understand this remark.
We should follow the same procedure as in Input parameters.

1. A value must be nil if not given and if default is not provided.
2. A value must be set to default if not changed.
3. A value must be set to given if changed.