fix(cli): Fix validation of --manual and --run-missed when setting policy

[PhracturedBlue]

As discovered while debugging #3344 when RunMissed was converted to a tri-state, the validation checks when setting --manual on the --global policy fail.

This is a small PR to address that and add an appropriate test for it.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (814738c) 75.88% compared to head (51888ad) 75.86%.
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3348      +/-   ##
==========================================
- Coverage   75.88%   75.86%   -0.02%     
==========================================
  Files         462      462              
  Lines       37082    37082              
==========================================
- Hits        28138    28133       -5     
- Misses       7020     7021       +1     
- Partials     1924     1928       +4     

Files	Coverage Δ
snapshot/policy/scheduling_policy.go	85.07% <0.00%> (ø)

... and 5 files with indirect coverage changes

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