sysutils/backuppc4: Update to 4.1.2

Changes: https://github.com/backuppc/backuppc/releases/tag/4.1.2

PR: 219020
Submitted by: Alexander Moisseev <moiseev@mezonplus.ru> (maintainer)
Approved by: garga (mentor)
Differential Revision: https://reviews.freebsd.org/D10978