Address pytest warnings (#3629)

* Address `boto` deprecation warnings

This commit eliminates the following warning:

../boto/ec2/connection.py:582:
  PendingDeprecationWarning: The current get_all_instances implementation will be replaced with get_all_reservations.

`boto` isn't likely to ever make good on this warning, but doing the replacement will
declutter the `moto` test output.

* Remove `invoke_lambda` tracebacks from unit test logging

If an exception is encountered, the details are returned in the response payload.
Printing the traceback was just adding noise to the pytest output.

* Use known AMIs in unit tests

This commit eliminates the following warning in the pytest output:

`PendingDeprecationWarning: Could not find AMI with image-id:ami-123456, in the near future this will cause an error.`

Known, pre-loaded AMI image ids are used instead of random ids that don't actually
exist in the moto backend.  The integrity of the tests is unaffected by this change.

A test has been added to provide explicit coverage of the PendingDeprecationWarning
raised when an invalid AMI image id is passed to moto.

tests/test_opsworks/test_instances.py

@@ -4,6 +4,7 @@ import sure  # noqa
 
 from moto import mock_opsworks
 from moto import mock_ec2
+from tests import EXAMPLE_AMI_ID
 
 
 @mock_opsworks
@@ -183,6 +184,7 @@ def test_ec2_integration():
     )["LayerId"]
 
     instance_id = opsworks.create_instance(
+        AmiId=EXAMPLE_AMI_ID,
         StackId=stack_id,
         LayerIds=[layer_id],
         InstanceType="t2.micro",