After WebRTC reconnect failure I'm stuck with SSH

[daonb]

Describe the bug
We need to add a Gate.onlySSH to support two reconnection flows -
the default one, targeted at webexec powered server and the SSH only one.
If onlySSH is true, there'll be no mention of WebRTC in the menus.

To get a gate out of SSH mode the user will edit the gate, select only
ssh field and presented with a prompt: "Only SSH (Y/n)?".

The initial setting of onlySSH will happen after the first SSH connect.
The user will be presented with a menu:

  Copy webexec install command and connect
  Let me in
  Let me in and always use SSH

If the user hasn't selected the third option, onlySSH will not be set
and he'll get the same menu each time he falls back to using ssh
allowing him to copy the install script later.

To Reproduce
Steps to reproduce the behavior:

1. Launch app
2. Tap on a gate with webexec install
3. disconnecd wifi stop webexec
4. reconnect wifi
5. get failure message
6. start webexec
7. try to reconnect using WebRTC

Screenshots
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Additional context
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