update ballot contract in the updated oracle config on prepare-update; simplify prepare-update;

[greenhat]

Close #204

[coveralls]

Pull Request Test Coverage Report for Build 3711347070

• 150 of 188 (79.79%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.7%) to 63.534%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
core/src/cli_commands/prepare_update.rs	150	188	79.79%
<!--	Total:	150	188	79.79%	-->

Files with Coverage Reduction	New Missed Lines	%
core/src/cli_commands/prepare_update.rs	2	66.67%
<!--	Total:	2		-->

Totals
Change from base Build 3649620024:	-0.7%
Covered Lines:	1981
Relevant Lines:	3118

---

💛 - Coveralls