update kernel4.19 and updategrub error

[lxd5866]

update kernel4.19 and updategrub is a dangerous operation， can we add a confirmation option to this step。I've had two boot failures because of this，and I prefer to do this manually

[houseonline]

The default kernel of some earlier versions of CentOS 7 lacks modules such as br_netfilter required by the kubernetes network, and the kernel needs to be optimized. Therefore, kube-install will upgrade and optimize the kernel of the CentOS 7 operating system by default. At some point, you may encounter the problem that the host cannot start.

In addition, the default kernel of CentOS 8, RHEL 8, SUSE Linux 15, Ubuntu 20, etc. does not have this problem, so the kernel will not be automatically upgraded, and it can be successfully installed and used!

[cloudnativer]

Thank you for your feedback!

We will add the skip upgrade kernel function in v0.7.3 and above. You can choose whether to skip the operating system kernel upgrade, and then you can optimize the centos7 kernel problem yourself.

[cloudnativer]

Screenshot of function preview of new version:

[lxd5866]

thanks