Replace the instancedirectory variable with an Instance class that holds
the directory and has a .path() to get paths relative to the instance
directory.
Rewrite the generateSSLcert lib to be async, use the sslCert and
sslPrivKey config entries and invoke it only if needed during master
server startup instead of in the post install script. Also add note to
the changelog covering both this and the fix in c645fac.
Hornwitser