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superseded by these changes and need not be backported.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:a794c32c13d2835ce5065f97fd2d76721c42fba1)
Merged-In: If2ad220dc2f4890ee67be62962a9b25d2f803e24
Change-Id: If2ad220dc2f4890ee67be62962a9b25d2f803e24