Add more tests for system calls to deal with bad buffers given to read and write

src/tests/userprog/exec-bad-ptr.ck

@@ -2,11 +2,7 @@
 use strict;
 use warnings;
 use tests::tests;
-check_expected ([<<'EOF', <<'EOF']);
-(exec-bad-ptr) begin
-(exec-bad-ptr) end
-exec-bad-ptr: exit(0)
-EOF
+check_expected ([<<'EOF']);
 (exec-bad-ptr) begin
 exec-bad-ptr: exit(-1)
 EOF