Initialize attr variables in Legacy.switch_get and LegacyFdbEntry.fdb…

…_entry_get (#1169)

When running unit tests for sairedis, there may be random test failures
for Legacy.switch_get and LegacyFdbEntry.fdb_entry_get. This is
happening because when doing the get call for
SAI_SWITCH_ATTR_DEFAULT_VIRTUAL_ROUTER_ID, the value isn't initialized
in this unit test function, with the assumption that it would contain
the actual value assuming the get call was successful. There's two
problems that happen:

1. Since a dummy SAI interface is being used for these tests, the get
call always succeeds (assuming that the attr list and count arguments
are valid), but the value for each attr is not modified at all.
2. Since this call returns a success, in
meta_generic_validation_post_get_objlist, it will see the value for the
attr (which is uninitialized memory) and complain that this value is
not valid for this attr.

Depending on the uninitialized memory there, the reference counter for
this OID may get incremented, and then when deleting the switch object,
it will complain that there's still objects present, because it thinks
this object exists.

To get around this, initialize `attr1` and `attr2` to make sure it's all
zeroes, and that some random OID won't get added to a reference list.

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

unittest/meta/TestLegacyFdbEntry.cpp

@@ -326,10 +326,14 @@ TEST(LegacyFdbEntry, fdb_entry_get)
 
     // correct 2 attributes
     sai_attribute_t attr1;
+    memset(&attr1, 0, sizeof(attr1));
     attr1.id = SAI_FDB_ENTRY_ATTR_TYPE;
+    attr1.value.oid = SAI_OBJECT_TYPE_NULL;
 
     sai_attribute_t attr2;
+    memset(&attr2, 0, sizeof(attr2));
     attr2.id = SAI_FDB_ENTRY_ATTR_BRIDGE_PORT_ID;
+    attr2.value.oid = SAI_OBJECT_TYPE_NULL;
     sai_attribute_t list[2] = { attr1, attr2 };
 
     status = g_meta->get(&fdb_entry, 2, list);

unittest/meta/TestLegacyOther.cpp

@@ -362,10 +362,14 @@ TEST(Legacy, switch_get)
     EXPECT_EQ(SAI_STATUS_SUCCESS, status);
 
     sai_attribute_t attr1;
+    memset(&attr1, 0, sizeof(attr1));
     attr1.id = SAI_SWITCH_ATTR_PORT_NUMBER;
+    attr1.value.oid = SAI_OBJECT_TYPE_NULL;
 
     sai_attribute_t attr2;
+    memset(&attr2, 0, sizeof(attr2));
     attr2.id = SAI_SWITCH_ATTR_DEFAULT_VIRTUAL_ROUTER_ID;
+    attr2.value.oid = SAI_OBJECT_TYPE_NULL;
     sai_attribute_t list[2] = { attr1, attr2 };
 
     status = g_meta->get(SAI_OBJECT_TYPE_SWITCH, switch_id, 2, list);