japanese/mozc-server: with build with python3

• limit python version to python 2.7
• remove duplicated python direct build dependency
• set correct python version in build scripts
• fix packaging by not installing to /root:
  
  ====>> Checking for filesystem violations... done ====>> Error: Filesystem touched during build: extra: root/.mozc

PR: 207937
Submitted by: Hiroo Ono <hiroo.ono+freebsd@gmail.com> (based on)
Approved by: maintainer timeout (14 days)