tree-wide: add ERRNO_IS_XATTR_ABSENT() helper

We check the same list of error codes on various xattr operations, and
we should on some more. Add a common helper for this purpose.

src/test/test-chown-rec.c

@@ -32,10 +32,8 @@ static const uint8_t default_acl[] = {
 static bool has_xattr(const char *p) {
         char buffer[sizeof(acl) * 4];
 
-        if (lgetxattr(p, "system.posix_acl_access", buffer, sizeof(buffer)) < 0) {
-                if (IN_SET(errno, EOPNOTSUPP, ENOTTY, ENODATA, ENOSYS))
-                        return false;
-        }
+        if (lgetxattr(p, "system.posix_acl_access", buffer, sizeof(buffer)) < 0)
+                return !ERRNO_IS_XATTR_ABSENT(errno);
 
         return true;
 }

src/test/test-xattr-util.c

@@ -46,7 +46,7 @@ TEST(getxattr_at_malloc) {
         fd = open("/", O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY);
         assert_se(fd >= 0);
         r = getxattr_at_malloc(fd, "usr", "user.idontexist", 0, &value);
-        assert_se(r == -ENODATA || ERRNO_IS_NOT_SUPPORTED(r));
+        assert_se(r < 0 && ERRNO_IS_XATTR_ABSENT(r));
 
         safe_close(fd);
         fd = open(x, O_PATH|O_CLOEXEC);