Rename "master key" => "password key"

Both names were used in the codebase and "password" was a clearer name
and also a better fit with inclusive language guidence.
https://source.android.com/setup/contribute/respectful-code

Bug: 161896447
Change-Id: I55a2e3538da7271fe59c0542191433b78bfa0cd4
2 files changed