Add hostname parameter for TCP probe (#981)

Add hostname parameter for TCP probe (#981)

This adds the ability to set the TLS server name for TCP probes using the hostname parameter,
just like #823 did for HTTP probes

* add hostname parameter for tcp probe
* only add servername if TLS is true
* add even if TLS isn't true in case of STARTTLS
* added test hostname parameter with TCP probe
* remove unnecessary function and inline assignment

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Signed-off-by: Lyas Spiehler <lspiehler@gmail.com>
Co-authored-by: Lyas Spiehler <lyas.spiehler@sapphirehealth.org>