crush/CrushTester: return EINVAL if crushtool returns non-zero

this backports a tiny part of ec02441, otherwise
CrushTester will return 1, and "ceph" cli will take it
as EPERM, which is miss leading, and fails
osd-crush.sh:TEST_crush_reject_empty.

Signed-off-by: Kefu Chai <kchai@redhat.com>

src/crush/CrushTester.cc

@@ -435,7 +435,7 @@ int CrushTester::test_with_crushtool(const string& crushtool,
   // something else entirely happened
   // log it and consider an invalid crush map
   err << "error running crushmap through crushtool: " << cpp_strerror(r);
-  return -r;
+  return -EINVAL;
 }
 
 namespace {