Make ghc -e not exit on valid import commands (#9905)

Summary:
Some Trues and Falses were mixed up due to Bool being used in
different senses in different parts of GHCi.

Test Plan: harbormaster; validate

Reviewers: austin

Reviewed By: austin

Subscribers: carter, thomie

Differential Revision: https://phabricator.haskell.org/D581

GHC Trac Issues: #9905

Conflicts:
	ghc/InteractiveUI.hs