snapuserd: Set taskprofile OtaProfiles

Since update-engine already has this profile set,
it is better to have similar profile for the daemon
so that threads don't run at high priority.

Additionally, lower the nice value for worker
threads.

No change in the OTA install time observed.

Bug: 237490659
Test: Full OTA on Pixel
Change-Id: I53ec8c647eb781965792683b04621e6fec5eb5f2
Signed-off-by: Akilesh Kailash <akailash@google.com>