enable switching user and running task command by using environment variable CCP_SWITCH_USER, which is to fix a bug that command, like "ulimit -l" on Ubuntu, is executed as root even if the runas user is specified as other user

nodemanager/scripts/StartTask.sh

@@ -34,9 +34,11 @@ fi
 if $CGInstalled; then
     groupName=$(GetCGroupName "$taskId")
     group=$CGroupSubSys:$groupName
-    cgexec -g "$group" /bin/bash $taskFolder/TestMutualTrust.sh "$taskId" "$taskFolder" "$userName" &&\
-    cgexec -g "$group" sudo -H -E -u $userName env "PATH=$PATH" /bin/bash $runPath
+    cgexec -g "$group" /bin/bash $taskFolder/TestMutualTrust.sh "$taskId" "$taskFolder" "$userName" && (\
+    [ "$CCP_SWITCH_USER" == "1" ] && (cgexec -g "$group" su - $userName -m -c "/bin/bash $runPath" || exit) ||\
+    cgexec -g "$group" sudo -H -E -u $userName env "PATH=$PATH" /bin/bash $runPath)
 else
-    /bin/bash $taskFolder/TestMutualTrust.sh "$taskId" "$taskFolder" "$userName" &&\
-    sudo -H -E -u $userName env "PATH=$PATH" /bin/bash $runPath
+    /bin/bash $taskFolder/TestMutualTrust.sh "$taskId" "$taskFolder" "$userName" && (\
+    [ "$CCP_SWITCH_USER" == "1" ] && (su - $userName -m -c "/bin/bash $runPath" || exit) ||\
+    sudo -H -E -u $userName env "PATH=$PATH" /bin/bash $runPath)
 fi