Fix tests to use correct fixtures for configuring (Apex)BootJars.

This is in preparation to r.android.com/1740313 where setting correct
variables would be enforced (i.e. apex and non-apex boot jars must be in
config.ApexBootJars and config.BootJars correspondingly).

Bug: 191369843
Test: m nothing
Change-Id: Ic86680c1f7af53d229083b2cc58beb3ceccb4b6a