disk_availability check: include submount storage

Fixes bug 1491566
https://bugzilla.redhat.com/show_bug.cgi?id=1491566

In order to determine how much storage is under a path, include any
mounts that are below it in addition to the path itself.

roles/openshift_health_checker/openshift_checks/disk_availability.py

@@ -1,6 +1,7 @@
 """Check that there is enough disk space in predefined paths."""
 
 import tempfile
+import os.path
 
 from openshift_checks import OpenShiftCheck, OpenShiftCheckException
 
@@ -121,11 +122,21 @@ class DiskAvailability(OpenShiftCheck):
 
         return {}
 
+    def find_ansible_submounts(self, path):
+        """Return a list of ansible_mounts that are below the given path."""
+        base = os.path.join(path, "")
+        return [
+            mount
+            for mount in self.get_var("ansible_mounts")
+            if mount["mount"].startswith(base)
+        ]
+
     def free_bytes(self, path):
         """Return the size available in path based on ansible_mounts."""
+        submounts = sum(mnt.get('size_available', 0) for mnt in self.find_ansible_submounts(path))
         mount = self.find_ansible_mount(path)
         try:
-            return mount['size_available']
+            return mount['size_available'] + submounts
         except KeyError:
             raise OpenShiftCheckException(
                 'Unable to retrieve disk availability for "{path}".\n'

roles/openshift_health_checker/test/disk_availability_test.py

@@ -96,6 +96,24 @@ def test_cannot_determine_available_disk(desc, ansible_mounts, expect_chunks):
             'size_available': 20 * 10**9 + 1,
         }],
     ),
+    (
+        ['oo_masters_to_config'],
+        0,
+        [{
+            'mount': '/',
+            'size_available': 2 * 10**9,
+        }, {  # not enough directly on /var
+            'mount': '/var',
+            'size_available': 10 * 10**9 + 1,
+        }, {
+            # but subdir mounts add up to enough
+            'mount': '/var/lib/docker',
+            'size_available': 20 * 10**9 + 1,
+        }, {
+            'mount': '/var/lib/origin',
+            'size_available': 20 * 10**9 + 1,
+        }],
+    ),
 ])
 def test_succeeds_with_recommended_disk_space(group_names, configured_min, ansible_mounts):
     task_vars = dict(
@@ -104,9 +122,10 @@ def test_succeeds_with_recommended_disk_space(group_names, configured_min, ansib
         ansible_mounts=ansible_mounts,
     )
 
-    result = DiskAvailability(fake_execute_module, task_vars).run()
+    check = DiskAvailability(fake_execute_module, task_vars)
+    check.run()
 
-    assert not result.get('failed', False)
+    assert not check.failures
 
 
 @pytest.mark.parametrize('name,group_names,configured_min,ansible_mounts,expect_chunks', [