This reverts commit 0267fe83b2.
Reason: it converted the tree to Windows line endings.
Updates #14299
Change-Id: I2271a61d43e99bd0bbcf9f4831e8783e570ba08a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
We have many function pointers that we replace for the duration of test and
restore it on test completion, add method to do that.
Signed-off-by: Maisem Ali <maisem@tailscale.com>