switch GetConfirmation()'s default to no

[alessio]

GetConfirmation() returns true if and only if the user's
input is confirmative.

The function is used in places where fat-fingering may cause
financial loss, e.g. gaiacli tx send command. Thus it seems
wiser to provide a conservative default in order to protect
users from accidental mistyping.

Closes: #4564

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry: clog add [section] [stanza] [message]
• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[okwme]

LGTM