Clean up password service.

Clean up password service.

* Remove PASSWORD_INFINITE_EXPIRATION_TIME from protocol* files.
* Add anonymous namespace in password-file.cpp
* Change PASSWORD_INFINITE_EXPIRATION_TIME value from -1 to max time_t.
* Remove cast between int/unsigned int/time_t in the code.

[Issue#]    N/A
[Bug]       N/A
[Cause]     N/A
[Problem]   N/A
[Solution]  N/A

[Verifcation] Build, run tests.

Change-Id: If41b690a7f4ac882281fc17bcdb79d20bfa9cb8d