Require TLS for transport layer when security is enabled for Trial licenses

[jkakavas]

Historically, we haven't enabled the transport TLS bootstrap check for trial licenses because:

• We want to make the experience of trial license users as easy as possible and configuring transport TLS was considered cumbersome.
• Trial licenses have a limited lifetime so that minimizes the impact of this potentially insecure configuration.

With security on by default project we are:

• Enabling security by default for basic and trial licenses
• We offer an easy, automated way for users to configure transport TLS
• As a consequence, enabling by default this bootstrap check for basic licenses.

It doesn't make much sense for us to enforce the bootstrap check on basic licenses but not on trial and given that the concerns that were driving the original decision are not there or have been partly alleviated, we should also enable the transport TLS bootstrap check on trial

[elasticmachine]

Pinging @elastic/es-security (Team:Security)

[elasticmachine]

Pinging @elastic/es-security (Team:Security)

[albertzaharovits]

We cannot allow Security without transport TLS because otherwise nodes without Security are then able to join the cluster, but we assume in several places that all nodes in the cluster have Security enabled (or not).

[jkakavas]

@albertzaharovits I assume the comment above was a 👍 to remove this leniency for trial licenses, right ?