xt_qtaguid: fix broken uid/gid range check

The existing test to check if current uid/gid is within
valid range is broken due to missing parenthesis.

Change-Id: I889ebbd0e2ea6a9426cb1509a2975e7107666407
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>