vendor: update containerd/continuity efbc4488d8fe1bdc16bde3b2d2990d9b3a899165

full diff: 26c1120b8d...efbc4488d8

Relevant changes:

- sysx/xattr: fix and improve
    - fix getxattrAll: change initial buffer size to 128 to prevent unneeded
      iterations and change the logic to get the real size in case we get ERANGE
      rather than doubling the buffer)
    - improve listxattrAll; refactor for readability, prevent calling `listxattr()`
      twice. Handle condition when attributes size is changed in between the two
      calls to listxattr().
- Remove Windows' Readlink fork
    - Drops support for Go 1.12 and under
- Fix sameFile() to recognize empty files as the same
    - fixes "Empty files can diff as "modified" even when they're not"

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/containerd/continuity/driver/driver_unix.go

@@ -131,8 +131,3 @@ func (d *driver) LSetxattr(path string, attrMap map[string][]byte) error {
 func (d *driver) DeviceInfo(fi os.FileInfo) (maj uint64, min uint64, err error) {
 	return devices.DeviceInfo(fi)
 }
-
-// Readlink was forked on Windows to fix a Golang bug, use the "os" package here
-func (d *driver) Readlink(p string) (string, error) {
-	return os.Readlink(p)
-}