Request focus when we set enabled true

When we are verifying the pin code, we invoke
setPasswordEntryInputEnabled(false). This sets isEnabled to false on the
password textview. Consequently, this is invoking clearFocus; however
when we set isEnabled back to true, we are not requesting focus. Ensure
that we request focus when textview is enabled again.

Fixes: 300250922
Test: with a physical keyboard, enter wrong password and retry. This
works before bug fix.
Test: with a physical keyboard, enter wrong pin and retry. It works with
the bug fix.
Flag: NONE

Change-Id: I32098c186339080873926196206d65fbe1a22952