Disable xattr feature on async-tar

This removes `xattr` dependency

We only care about backed up file contents, not attributes.

Cargo.lock

@@ -372,7 +372,6 @@ dependencies = [
  "libc",
  "pin-project",
  "redox_syscall",
- "xattr",
 ]
 
 [[package]]
@@ -4186,15 +4185,6 @@ dependencies = [
  "zeroize",
 ]
 
-[[package]]
-name = "xattr"
-version = "0.2.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "244c3741f4240ef46274860397c7c74e50eb23624996930e484c16679633a54c"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "zeroize"
 version = "1.3.0"