Always no quotes for $() statement.
We don't need quotes to hold blanks in result:
# i=$(echo 1 2 3)
# echo $i
1 2 3
#
These quotes can make something wrong in some case:
# i=$(echo '!')
#
# i="$(echo '!')"
-bash: !: event not found
#
No real problem for current code, only to use a better code style.
Change-Id: I0f43bb936f956c99603dc15aaad9db851ecf0acd
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>