[DO NOT MERGE] Fix Heap use after free in clearkey getSecureStops

Security Vulnerability fix: Heap use after free in getSecureStops
in android.hardware.drm@1.1-service.clearkey

Test: adb shell ps | grep clearkey
  pid ID does not change after running drmpoc

Test: sts
  ANDROID_BUILD_TOP= ./android-sts/tools/sts-tradefed run sts-engbuild-no-spl-lock -m StsHostTestCases --test android.security.sts.Poc19_07#testPocBug_137878930

bug: 137878930
Merged-In: I78b2dc2bccde238a06398b3733cea8e574ea8ee7
Change-Id: I4fa2f0ad3f3360812987223f507a7394357080b3