set subject name in I2PControl certificate

[pobregat0]

The certificate i2pd makes for I2PControl has an empty subject: the name is
built and then set as the issuer only. OpenSSL 3 does not take it for self
signed, tries to build a chain and refuses the sha1 signature of that "CA":

I2PControl: Failed to load ceritifcate: ca md too weak (SSL routines). Recreating
I2PControl: Can't load certificates
I2PControl: Handshake error: no shared cipher (SSL routines)

so the service never starts at all. A plain self signed sha1 certificate made
by openssl loads on the same machine without a word, so the signature algorithm
is not the cause and is left alone here.

With the subject set the certificate loads and requests are answered, sha1 kept.
A certificate saved by an older version is replaced on start by the code that is
already there. Checked on Debian 13, OpenSSL 3.5.6.