GOCBC-996: Remove [] from id for CollectionMap.At and Exist

Motivation
-----------
The Map data structure is using invalid paths for At and Exists.
This is causing these functions to be unuseable. They wrap
the id in `[<id>]` which looks like a copy and paste bug from
the list/set data structures.

Changes
-------
Don't wrap the id in `[<id>]` for At and Exists for the map
data structure.

Change-Id: I5f7dfcb506c260603405e5b6b8e0eabcb703425b
Reviewed-on: http://review.couchbase.org/c/gocb/+/137041
Reviewed-by: Charles Dixon <chvckd@gmail.com>
Tested-by: Charles Dixon <chvckd@gmail.com>

collection_ds.go

@@ -166,7 +166,7 @@ func (cl *CouchbaseMap) Iterator() (map[string]interface{}, error) {
 // At retrieves the item for the given id from the map.
 func (cl *CouchbaseMap) At(id string, valuePtr interface{}) error {
 	ops := make([]LookupInSpec, 1)
-	ops[0] = GetSpec(fmt.Sprintf("[%s]", id), nil)
+	ops[0] = GetSpec(id, nil)
 	result, err := cl.collection.LookupIn(cl.id, ops, nil)
 	if err != nil {
 		return err
@@ -202,7 +202,7 @@ func (cl *CouchbaseMap) Remove(id string) error {
 // Exists verifies whether or a id exists in the map.
 func (cl *CouchbaseMap) Exists(id string) (bool, error) {
 	ops := make([]LookupInSpec, 1)
-	ops[0] = ExistsSpec(fmt.Sprintf("[%s]", id), nil)
+	ops[0] = ExistsSpec(id, nil)
 	result, err := cl.collection.LookupIn(cl.id, ops, nil)
 	if err != nil {
 		return false, err

collection_ds_test.go

@@ -341,6 +341,13 @@ func (suite *IntegrationTestSuite) TestMapCrud() {
 		suite.T().Fatalf("Expected cMap size to be 4 but was %d", size)
 	}
 
+	var test3Val string
+	err = cMap.At("test3", &test3Val)
+	suite.Assert().Nil(err, err)
+	suite.Assert().Equal("test3val", test3Val)
+
+	suite.Assert().True(cMap.Exists("test3"))
+
 	iter, err := cMap.Iterator()
 	if err != nil {
 		suite.T().Fatalf("Failed to get iterator for cMap %v", err)
@@ -362,6 +369,8 @@ func (suite *IntegrationTestSuite) TestMapCrud() {
 		suite.T().Fatalf("Failed to remove from cMap %v", err)
 	}
 
+	suite.Assert().False(cMap.Exists("test1"))
+
 	size, err = cMap.Size()
 	if err != nil {
 		suite.T().Fatalf("Failed to get size of cMap %v", err)