Improve TestLoader's helper method find_objects_by_name

This gives you better indication of what's happening.

```
======================================================================
FAIL: test_row_values (ion.processes.bootstrap.test.test_loader.TestLoader)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/asadeveloper/Documents/Dev/code/coi-services/ion/processes/bootstrap/test/test_loader.py", line 101, in test_row_values
    dp = self.find_object_by_name('Test DP L0 CTD', RT.DataProduct)
  File "/Users/asadeveloper/Documents/Dev/code/coi-services/ion/processes/bootstrap/test/test_loader.py", line 76, in find_object_by_name
    self.assertGreaterEqual(len(objects), 1)
AssertionError: 0 not greater than or equal to 1
```