ASan: Fixed memory leak

This change frees the |struct minijail| in minijail0:

=================================================================
==31408==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 768 byte(s) in 1 object(s) allocated from:
    #0 0x7f69b789f79a in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9879a)
    #1 0x4030cb in main minijail0.c:592
    #2 0x7fffe06c1724  (<unknown module>)

SUMMARY: AddressSanitizer: 768 byte(s) leaked in 1 allocation(s).

Bug: None
Test: ./minijail0 (compiled with -fsanitize=address)
Change-Id: If01e1174b736f6d19abe3597318bed4dc3fb013a

minijail0.c

@@ -628,5 +628,9 @@ int main(int argc, char *argv[])
 		info("not running init loop, exiting immediately");
 		return 0;
 	}
-	return minijail_wait(j);
+	int ret = minijail_wait(j);
+#if defined(__SANITIZE_ADDRESS__)
+	minijail_destroy(j);
+#endif /* __SANITIZE_ADDRESS__ */
+	return ret;
 }