fix: Fix ippool max mask length and first cidr error

Created by: leoendless

Signed-off-by: leoliu leoliu@yunify.com

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #https://github.com/kubesphere/console/issues/1671 #https://github.com/kubesphere/console/issues/1668

Special notes for reviewers:

Additional documentation, usage docs, etc.: