Ignore 'dynamic' addr flag on bridge configuration

When setting the bridge up, if that flag is present but not
ignored, the delete command will fail and may leave the
interface and the bridge in an inconsistent state.

Closes-Bug: #1274611
Related-Bug: #1077066
Change-Id: Iff65d61d724d0de5d8173ac37f7f748aa23e5d8b
(cherry picked from commit 0d447f6edd406547e828c592823ac6624e56e91f)
Merge "Ignore 'dynamic' addr flag on bridge configuration" into stable/havana