nixos/netbird: fixes login not working properly on first login
When the netbird client is initially started, the first status
command will return a seemingly normal output which contains
`Peers 0/0 Connected`. This is treated as if already logged in,
which is not the case, as a subsequent status command will
display the `NeedsLogin` message. This PR fixes that, by
checking for `: Connected`, which is used in e.g. `Managament: Connected`,
(cherry picked from commit a7d4d7418ba835b695de85e4d82c2ec9423ba146)