[eCCT] Ensure OTR cookies are stored before loading initial OTR tab.

Prior to this, the tab was being created before the cookies were restored,
so the initial page load would not be using the cookie state.

This does result in delaying the initial load, but this only applies for
OTR CCT instances that had saved instance state. So this should only apply
to users reselecting from recents.

Bug: 360159401
Change-Id: I7169d6e3d6726fbdcb7220d7941c97f3a7fb3811
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5877701
Commit-Queue: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1358565}