optimize the install-mysql-rbr.py

[jd-zhang]

*Issue migrated from trac ticket # 850 www.kunlunbase.com *

component: kunlun-storage | priority: major

2022-06-24 14:36:46: snow@zettadb.com created the issue

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1. take a break after initialize the MySQL datadir before proceeding installation\
2. modify post_install.sh , template-rbr-small.cnf

[jd-zhang]

2022-06-24 17:59:13: snow@zettadb.com edited the issue description