--quick-validation flag has bad hyperparameter selection

[MatthewThe]

https://github.com/percolator/percolator/commit/6b325c23665d6ff64b0ff1ce28371424dcc88d17 seems to have introduced a bug in the --quick-validation flag.

Previously, the best cpos and cfrac were found using a grid search in the first cross validation set. These optimal values were then reused in the remaining folds. After the commit, cpos=1 and cfrac=1 were hard coded for all folds. This can lead to suboptimal results.

This behavior affects v3.05 and beyond.