Enforce argument check on setThreadGroup and friends

in android/os/Process.java
@param group The target group for this thread from THREAD_GROUP_*.

However, there is no boundary check on this.
and "SchedPolicy sp = (SchedPolicy) grp;" is an undefined behavior.

Fixes: 142097996
Test: boot
Change-Id: I8f6f9f5527903aa8b311c419a2ec803b4894cf8f