Improve audio sharing password handling

This is a backport of ag/31824318.  ag/31424453 against the same bug is
superseded by these changes and need not be backported.

Test: atest
Bug: 389127608
Ignore-AOSP-First: security
Tag: #security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:5d3f4de60e49dabd1fcafac8db352266e5cf1863)
Merged-In: If2ad220dc2f4890ee67be62962a9b25d2f803e24
Change-Id: If2ad220dc2f4890ee67be62962a9b25d2f803e24