do not hardcode dsaparam numbits

[Jose]

icecertutils/IceCertUtils/OpenSSLCertificateUtils.py

Line 109 in 5ba680b

 self.run("openssl", "dsaparam", 1024, outform="PEM", out=self.keysize) 

We should not hardcode the numbits used to generated the DSA parameter, furthermore 1024 is not accepted with recent OpenSSL versions that require to use 2048 bit or more.