lobster: clear insertion after successful and unsuccessful commit

Ash currently crashes when focusing on an input field after an unsuccessful commit. This crash occurs because the callback function, intended to execute once after insertion, is triggered a second time.

It turns out that unsuccessful insertion commits are not cleared, and the queued insertion persists after unsuccessful commits. This leads to the aforementioned crashes. This change ensures the queued insertion is always cleared after any commit, regardless of whether it is successful.

Bug: b:377222437
Change-Id: I6498b592bdee7a8f5347a65fcebd8f9e27bbe9aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5988730
Reviewed-by: Curtis McMullan <curtismcmullan@chromium.org>
Commit-Queue: Chuong Ho <hdchuong@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1377991}