[FrameworkBundle] Reuse definition variable in FormPass
merged branch franmomu/reuse_variable_formpass (PR #7464)

This PR was merged into the 2.1 branch.

Discussion
----------

[FrameworkBundle] Reuse definition variable in FormPass

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
-------

f52320d [FrameworkBundle] Reuse definition variable in FormPass