Editing multiple racks doesn't validate devices out of bound

[Zimeon-]

Issue type

[ ] Feature request
[X] Bug report
[ ] Documentation

Environment

• Python version:
• NetBox version: 2.1.4

Description

If you edit multiple racks and make them smaller, there's no validation to check if there are any devices left out of bound of the new rack size.

In example you can edit multiple racks from the size of 42U to say 20U, and if a device was previously at rack on position 30, this rack will not load anymore and an error is given.

Validation is done when editing a single rack and this issue does not occur then.

edit: words.

[jeremystretch]

Somewhat related to #1136

[jeremystretch]

Fixed via #1136 (b65d994)