am: set to top-app process group only for instrument

Bug: 379892006 
Bug: 383813628
Change-Id: I6cf725f659cb1936c40665e72e5f739dea66de0e
Test: Build
Flag: NONE for a script change
diff --git a/cmds/am/am.sh b/cmds/am/am.sh
index 76ec214..f099be3 100755
--- a/cmds/am/am.sh
+++ b/cmds/am/am.sh
@@ -1,11 +1,10 @@
 #!/system/bin/sh
 
-# set to top-app process group
-settaskprofile $$ SCHED_SP_TOP_APP >/dev/null 2>&1 || true
-
 if [ "$1" != "instrument" ] ; then
     cmd activity "$@"
 else
+    # set to top-app process group for instrument
+    settaskprofile $$ SCHED_SP_TOP_APP >/dev/null 2>&1 || true
     base=/system
     export CLASSPATH=$base/framework/am.jar
     exec app_process $base/bin com.android.commands.am.Am "$@"