Retain hal_drm_server attribute for neverallow tests

Addresses:
Warning!  Type or attribute hal_drm_server used in neverallow
undefined in policy being checked.

Bug: 67296580
Test: Build
Merged-In: I1092aff40da9dcf09bd044400bedd1f549eb7e38
Change-Id: I07f9825536637a21a91c77e87366861503f6ebac