Get rid of --voms cms when doing myproxy-init

Bugfix request from Brian, the problem seems to be that VOMS will not extension renewal later in the chain if --voms cms is used for myproxy-init:

    command : source /afs/cern.ch/cms/LCG/LCG-2/UI/cms_ui_env.sh && env X509_USER_PROXY=/data/certs/creds/fc479abdf4599c660226aa7e521e56922b971626 voms-proxy-init -noregen -voms cms:/cms/uscms/Role=cmsuser -out /data/certs/creds/fc479abdf4599c660226aa7e521e56922b971626 -bits 1024 -valid 167:59
     output : Your identity: /DC=com/DC=DigiCert-Grid/O=Open Science Grid/OU=People/CN=Brian Bockelman/CN=proxy/CN=proxy/CN=proxy
    Contacting  voms.cern.ch:15002 [/DC=ch/DC=cern/OU=computers/CN=voms.cern.ch] "cms" Done
    Creating proxy  Done
    Your proxy is valid until Wed Dec 11 04:22:52 2013

     error:
    Warning: cms : your certificate already contains attributes, only a subset of them can be issued.