Lists returned from OS aren't mutable.

Data returned via ParceledListSlice is a snapshot of data from the
system, and should not be mutated directly.

In particular, this can cause developer confusion if they call
Collection.remove(), which doesn't actually mutate the value in the
system.  There are other mutation APIs that developers should be
using instead, such as JobScheduler.cancel().

Test: builds, boots, common operations work
Bug: 27856974
Change-Id: I72528dee4d79e483aa295bd91d1ed80d0d72d21c