Add libprocessgroup dependency

Because set_sched_policy is moved into libprocessgroup an additional
dependency is required for its users. libframeworksnettestsjni requires
libprocessgroup otherwise com.android.frameworks.tests.net fails with
error:
dlopen failed: library "libprocessgroup.so" not found

Exempt-From-Owner-Approval: janitorial

Bug: 111307099
Test: builds, boots

Change-Id: Ia8bc5b447efa568fd1c822746919fa1496cc42a6
Signed-off-by: Suren Baghdasaryan <surenb@google.com>