Improve parsing of string values that represents booleans during block device mapping construction (#3073)

* convert str into bool

* Fix python2

* Fix python2

* pylint

moto/ec2/responses/instances.py

@@ -13,6 +13,7 @@ from moto.elbv2 import elbv2_backends
 from moto.core import ACCOUNT_ID
 
 from copy import deepcopy
+import six
 
 
 class InstanceResponse(BaseResponse):
@@ -283,15 +284,15 @@ class InstanceResponse(BaseResponse):
             device_template["Ebs"]["VolumeSize"] = device_mapping.get(
                 "ebs._volume_size"
             )
-            device_template["Ebs"]["DeleteOnTermination"] = device_mapping.get(
+            device_template["Ebs"]["DeleteOnTermination"] = self._convert_to_bool(
-                "ebs._delete_on_termination", False
+                device_mapping.get("ebs._delete_on_termination", False)
             )
             device_template["Ebs"]["VolumeType"] = device_mapping.get(
                 "ebs._volume_type"
             )
             device_template["Ebs"]["Iops"] = device_mapping.get("ebs._iops")
-            device_template["Ebs"]["Encrypted"] = device_mapping.get(
+            device_template["Ebs"]["Encrypted"] = self._convert_to_bool(
-                "ebs._encrypted", False
+                device_mapping.get("ebs._encrypted", False)
             )
             mappings.append(device_template)
 
@@ -308,6 +309,16 @@ class InstanceResponse(BaseResponse):
         ):
             raise MissingParameterError("size or snapshotId")
 
+    @staticmethod
+    def _convert_to_bool(bool_str):
+        if isinstance(bool_str, bool):
+            return bool_str
+
+        if isinstance(bool_str, six.text_type):
+            return str(bool_str).lower() == "true"
+
+        return False
+
 
 BLOCK_DEVICE_MAPPING_TEMPLATE = {
     "VirtualName": None,

tests/test_ec2/test_instances.py

@@ -128,7 +128,35 @@ def test_instance_terminate_discard_volumes():
 
 
 @mock_ec2
-def test_instance_terminate_keep_volumes():
+def test_instance_terminate_keep_volumes_explicit():
+
+    ec2_resource = boto3.resource("ec2", "us-west-1")
+
+    result = ec2_resource.create_instances(
+        ImageId="ami-d3adb33f",
+        MinCount=1,
+        MaxCount=1,
+        BlockDeviceMappings=[
+            {
+                "DeviceName": "/dev/sda1",
+                "Ebs": {"VolumeSize": 50, "DeleteOnTermination": False},
+            }
+        ],
+    )
+    instance = result[0]
+
+    instance_volume_ids = []
+    for volume in instance.volumes.all():
+        instance_volume_ids.append(volume.volume_id)
+
+    instance.terminate()
+    instance.wait_until_terminated()
+
+    assert len(list(ec2_resource.volumes.all())) == 1
+
+
+@mock_ec2
+def test_instance_terminate_keep_volumes_implicit():
     ec2_resource = boto3.resource("ec2", "us-west-1")
 
     result = ec2_resource.create_instances(