Increase the default auto-enrollment upload bits to 6.
Increase the default auto-enrollment upload bits to 6.

The auto-enrollment check uploads a limited number of bits from the
hash of the device serial number to determine the device's bucket on the
server-side. The buckets are now large enough that an additional bit is
required.

BUG=chromium:233111
TEST=Auto-enrollment still works.

Change-Id: I4acd37b06c21a02f0606f91aa0526e901c746d49
Reviewed-on: https://gerrit.chromium.org/gerrit/48492
Reviewed-by: Mattias Nissler <f2124f8e21694335a48d099eb9510c5c4dda0d0b@chromium.org>
Commit-Queue: Joao da Silva <aefd81ab904d210b7e0c393e2308ddec571f4e12@chromium.org>
Tested-by: Joao da Silva <aefd81ab904d210b7e0c393e2308ddec571f4e12@chromium.org>

chadversary/chromiumos.platform.login_manager,chadversary/chromiumos.platform.login_manager,chadversary/chromiumos.platform.login_manager