use prevPath in data.Collection (#1943)

## Type of change

- [x] 🐛 Bugfix

## Issue(s)

* #1777

## Test Plan

- [x] 💪 Manual

src/internal/connector/exchange/exchange_data_collection.go

@@ -158,7 +158,7 @@ func (col *Collection) FullPath() path.Path {
 // TODO(ashmrtn): Fill in with previous path once GraphConnector compares old
 // and new folder hierarchies.
 func (col Collection) PreviousPath() path.Path {
-	return nil
+	return col.prevPath
 }
 
 func (col Collection) State() data.CollectionState {

src/internal/data/data_collection_test.go

@@ -12,6 +12,7 @@ import (
 
 type mockColl struct {
 	p     path.Path
+	prevP path.Path
 }
 
 func (mc mockColl) Items() <-chan Stream {
@@ -23,7 +24,7 @@ func (mc mockColl) FullPath() path.Path {
 }
 
 func (mc mockColl) PreviousPath() path.Path {
-	return nil
+	return mc.prevP
 }
 
 func (mc mockColl) State() CollectionState {
@@ -54,7 +55,7 @@ func (suite *CollectionSuite) TestResourceOwnerSet() {
 			ToDataLayerExchangePathForCategory("tid", resource, path.EventsCategory, false)
 		require.NoError(t, err)
 
-		return mockColl{p}
+		return mockColl{p, nil}
 	}
 
 	table := []struct {