Fix cursor-jumping with `autoSelectFirst`

`autoSelectFirst` was causing the cursor to jump by resetting the
input value to `currentValue` regardless of necessity. This commit
fixes that by checking the value of the input field before updating.

Change-Id: I151c344e524d0821ebb978a8b2cf5461e509ab8c
Reviewed-on: https://gerrit.causes.com/19457
Reviewed-by: Henric Trotzig <henric.trotzig@causes.com>
Tested-by: Tony Wooster <tony.wooster@causes.com>