Fix typo for run_tests.sh -S option

This patch fixes a typo of getopt's arguments. If the second 's' option letter
is not 'S', -S option is not recognized.

Fix bug 1161921

Change-Id: I0b5a372e7257b9319b350131303c1a9f51b57eb5
Merge "Fix typo for run_tests.sh -S option"