Build Environment accepts duplicate name during edit

Steps to reproduce:
1. add a build environment (name="env1")
2. add another build environment (name="env2")
3. edit the build environment in #2 and change the name to "env1"

Observed behavior:

• Duplicates are not accepted when adding build environments.
• Duplicates are accepted when editing build environments.

Expected behavior:

• Duplicates should not be accepted when editing a build environment.