examples/testcase: fix build error about unused variable
examples/testcase: fix build error about unused variable

If you only enable 'EXAMPLES_TESTCASE' and do not enable detailed
options, you will not use the 'pid' variable. This can cause build
errors.

Change-Id: Ib87cd50b7adef2dde0e3493e0db8fca47aa772f8
Signed-off-by: Junhwan Park <7fee488b6f78fc50b291ffc7d10428788977e877@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT