Fix bug in dev_cli script's db-generate command

[joelvdavies]

Description

Make db-generate dump when -d or --dump is supplied rather than when they aren't. Also it only cleared the test database as I had forgotten to specify ims.

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• [ ] Review code
• [ ] Check Actions build
• [ ] Review changes to test coverage

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