Validate ros cloud-config as much as possible

[niusmallnan]

Now we can use ros config validate to to validate ros cloud-config, this is not enough. In particular, the user manually modifies the config. If the wrong configuration is added, it may cause the startup to fail.

I think we need to enhance the experience and give users friendly tips.

Such as the following:

1. before the reboot or shutdown
2. before ros install -c
3. others if needed

[rootwuj]

Tested with rancher/os:v1.5.2-rc1 from May 21
Verified fixed

Test:

• Set the wrong cloud-config
• Run the reboot or shutdown command
• Run sudo ros install -c

Result:

• Display error message and command is not being run.