Typo fixes in comments

Correct spelling of words in source code comments.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

docs/storage/driver/gcs/gcs.go

@@ -285,7 +285,7 @@ func (d *driver) WriteStream(context ctx.Context, path string, offset int64, rea
 	if err != nil {
 		return nn, err
 	}
-	// wc was closed succesfully, so the temporary part exists, schedule it for deletion at the end
+	// wc was closed successfully, so the temporary part exists, schedule it for deletion at the end
 	// of the function
 	defer storageDeleteObject(gcsContext, d.bucket, partName)
 

docs/storage/driver/storagedriver.go

@@ -133,7 +133,7 @@ func (err InvalidOffsetError) Error() string {
 }
 
 // Error is a catch-all error type which captures an error string and
-// the driver type on which it occured.
+// the driver type on which it occurred.
 type Error struct {
 	DriverName string
 	Enclosed   error

docs/storage/driver/testsuites/testsuites.go

@@ -158,7 +158,7 @@ func (suite *DriverSuite) TestInvalidPaths(c *check.C) {
 
 	for _, filename := range invalidFiles {
 		err := suite.StorageDriver.PutContent(suite.ctx, filename, contents)
-		// only delete if file was succesfully written
+		// only delete if file was successfully written
 		if err == nil {
 			defer suite.deletePath(c, firstPart(filename))
 		}