Retry router removal on conflict

Manila injects share network to tenant router underhood,
the interface removal is asynchronous in manila. This is
only one example when conflict migh happen. Since rest assumes
we can retry on Conflicts, do it here.

Related-Prod: PRODX-27590
Change-Id: I3c284673abf13e2c01ebca047c353de1207caf12
(cherry picked from commit 1ea945680d2a7731ebe16d322721b79b4fb13b26)
3 files changed