No client override during migrate:make

[OlivierCavadenti]

• During migrate:make client is set to 'sqlite3' only if client
  is not setted in options and configuration.
• Closes Knex imports sqlite in migrate:make when told to use pg #5102

[coveralls]

Coverage increased (+0.01%) to 92.273% when pulling c0dcb78 on OlivierCavadenti:fix-client-override into 43dcc79 on knex:master.

[kibertoad]

Tests are failing.

[OlivierCavadenti]

(by the way we can see that coveralls comments works :D. I switch for detailed to short comments)

[sholladay]

@kibertoad this PR and release 1.0.6 did not fix the problem.

At a glance, I believe the reason that the new test in this PR did not catch the problem is because, unlike many Knex users' projects, the Knex repo itself does have @vscode/sqlite3 installed. So you'll never get the "cannot find module" error, because Node can find it. And the test doesn't truly check which client is being used, even though it probably should.

Ideally, the testing infrastructure would scaffold a new temporary directory with its own package.json (etc) in /tmp for each test or at least each suite, to more easily reproduce a true user experience.