Fix edge case short circuit logic in binomial distro inverse.

[jzmaddock]

Fixes: #1397

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.35%. Comparing base (f724aec) to head (31197ca).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1398   +/-   ##
========================================
  Coverage    95.35%   95.35%           
========================================
  Files          825      825           
  Lines        68310    68310           
========================================
+ Hits         65138    65139    +1     
+ Misses        3172     3171    -1     

Files with missing lines	Coverage Δ
include/boost/math/distributions/binomial.hpp	86.56% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[dschmitz89]

Thanks @jzmaddock , this was so quick I barely noticed.