net/zerotier: update 1.2.8 to 1.2.10

include 3 upstream bugs related to large environments:

• Fix bug loading moons.d/ files for federated root operation.
• Fix compile problem with ZT_DEBUG on some versions of clang
• Fix slow network startup bug related to loading of networks.d/ cache files

improve daemon functionality:

• improve rc.d dependencies by requiring devfs instead of netif
• use daemon(8) to capture debug logging to syslog if > FreeBSD 11.1R and if compiled with debugging option
• let rc.d script load if_tap if not already present
• add reminder for users about sysctls to avoid race conditions at boot time

Reviewed by: mat
Approved by: jrm
Differential Revision: https://reviews.freebsd.org/D15534