Resolve symlink issue.

If there is certain symlink in the container image like this:

/A --> /X/Y/Z

AND if the "/X/Y/Z" doesn't exists on the host OS, then the current
invocation to os.Stat will give errors saying that the "Could not
obtain size for /X/Y/Z". This is because that it will follow the
link to check the /X/Y/Z on the host. That is improper.

The proper behaviour should be:
From the perspective of the symlink inside the container image, the
valid target file it pointing to is always some "existing file" in
the container image.
From the perspective of the host OS, it should just respect the
"closure" of the file system inside the container image.

To resolve it, instead of the os.Stat, we can use os.Lstat which
will not follow the link to check the target file.

Signed-off-by: zhongjie <zhongjie.shi@intel.com>

Author: intelzhongjie

pkg/util/fs_utils.go

@@ -39,7 +39,7 @@ type DirectoryEntry struct {
 }
 
 func GetSize(path string) int64 {
-	stat, err := os.Stat(path)
+	stat, err := os.Lstat(path)
 	if err != nil {
 		logrus.Errorf("Could not obtain size for %s: %s", path, err)
 		return -1
@@ -56,7 +56,7 @@ func GetSize(path string) int64 {
 
 //GetFileContents returns the contents of a file at the specified path
 func GetFileContents(path string) (*string, error) {
-	if _, err := os.Stat(path); os.IsNotExist(err) {
+	if _, err := os.Lstat(path); os.IsNotExist(err) {
 		return nil, err
 	}
 
@@ -145,11 +145,11 @@ func CheckSameSymlink(f1name, f2name string) (bool, error) {
 
 func CheckSameFile(f1name, f2name string) (bool, error) {
 	// Check first if files differ in size and immediately return
-	f1stat, err := os.Stat(f1name)
+	f1stat, err := os.Lstat(f1name)
 	if err != nil {
 		return false, err
 	}
-	f2stat, err := os.Stat(f2name)
+	f2stat, err := os.Lstat(f2name)
 	if err != nil {
 		return false, err
 	}