Trying to SSH when SELinux is enforced results in errors like:
```
➜ ~ ssh ec2-user@<ip>
Last login: Thu Jun 1 22:51:44 from <ip2>
ec2-user: no shell: Permission denied
Connection to <ip> closed.
```
while the `/var/log/audit/audit.log` has
```
type=AVC msg=audit(1685661291.067:465): avc: denied { transition } for pid=5296 comm="login" path="/usr/bin/bash" dev="nvme0n1p1" ino=2564 scontext=system_u:system_r:unconfined_service_t:s0 tcontext=unconfined_u:unconfined_r:unconfined_t:s0 tclass=process permissive=0
```
The right fix here would be to somehow install the appropriate context when
tailscale is installed on host, but until we figure out a way to do that
stop using the `login` cmd in these situations.
Updates #4908
Signed-off-by: Maisem Ali <maisem@tailscale.com>
2ae670eb71