fibs: Limit the WARNING message to only once when setting up with multiple fibs
In main [1] this warning message is suppressed but no plans to MFC the
change as the message may be still useful for users that upgrade from
older releases to 14.x or 13.x. Well emitting this warning message every
time increasing the fib number is confusing for users not for the feature
net.add_addr_allfibs, let's limit it to be printed only once.
- a48f7a2eb90b fibs: Suppress the WARNING message for setups with multiple fibs
This is a direct commit to stable/14 and stable/13.
PR: 280097
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D46204
(cherry picked from commit 352dd826ffdd88d26744023fe8bcff795bdf64d8)