Notify users when XO gets low on RAM

[ydirson]

Is your feature request related to a problem? Please describe.

When low on RAM, XO starts to be slow to respond, then ultimately the service restarts. The reason is not readily visible to users of the Web UI. The /xoa/support check for memory also reports "OK" while battling to stay alive.

Describe the solution you'd like

A big alert of some sort that users cannot miss they have a RAM problem and have to act or get sb to act on it.

[julien-f]

1. xoa check already checks whether the appliance has less than 25% memory free
2. are xoa check issues visible enough in the UI?
3. should these warnings also be sent by emails?

[ydirson]

If /xoa/support reflects xoa check there there is likely a problem somewhere in the chain?