murmur/Cert: check for 'Murmur Autogenerated Certificate' prefix instead of explicit version in self-signed cert check.
murmur/Cert: check for 'Murmur Autogenerated Certificate' prefix instead of explicit version in self-signed cert check.

This commit changes our check for whether a server is using a self-signed
certificate to check for the prefix 'Murmur Autogenerated Certificate'.

Previously, we would only check for 'Murmur Autogenerated Certificate v2'.
(The previous version, 'Murmur Autogenerated Certificate' is no longer valid,
so is not considered in this context.)

This will allow us to bump the version in the certificate, without needing
to update our code to know about these bumps.

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