[Regression] Update LTP tests to the upstream version

LTP test kill12 was removed from the PASSED list because it incorrectly
works unders Glibc 2.19. This improves stability of our LTP regression.

LibOS/shim/test/apps

@@ -1 +1 @@
-Subproject commit b79274d94c960e60e67261ebd5937fa9be63e135
+Subproject commit a60b38bad6815032b5d55e86a5b20036bb8a89bb