Fixed a racecondition when creating notification headers

Previously we were modifying the extras of a shared notification
during the notification creation, which breaks if multiple builders
are accessing the same notification. We're now passing these options
as parameters into the various functions.

Test: create low priority group / notification / observe normal behavior
Change-Id: I2aaa5632cff55a87937a2bb3f947f15555d2e897
Fixes: 117150727