databases/mysql55-server: Adapt ${name}_limits to the new resource limiting mechanics for services

[0mp]

Summary

Thanks to the recent change to rc.subr(8) it is no longer necessary to
define a resource limiting logic in service scripts. limits(1) is now run
by default and its configuration is handled via the "${name}_limits"
variable.

Unfortunately, there is a collision of variable names. The service scripts
are broken on FreeBSD version with that new change (>= 12.0).

The patch preserves the old behavior on the systems without the rc.subr(8)
modification.

Approved by:    maintainer timeout

• https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227228

Test Plan

• poudriere
  • i386
    • 11.2
    • 12.0-BETA2
  • amd64
    • 11.2
    • 12.0-BETA2