Clear Gatekeeper state before a new enrollment

On some devices gatekeeper would fail after certain enrollments due to
some persistent state left around. Call clearSecureUserId() to clear
these state would solve the problem.

Bug: 37704110
Test: execute adb shell cmd lock_settings set-password --old 1234 1234 many times
Change-Id: I0344d6e5bf8b08dd7f1314451bc6d5e3c8c68bab
Merged-In: I0344d6e5bf8b08dd7f1314451bc6d5e3c8c68bab