Bug 3641: v3 factory broken for v2 frontends

46eabe9baf352de579371d6dcf048bc808f84c56 cut out the other half of the
else condition that adds the x509 proxies to security_credentials.
Without this fix, a v3 glide factory entry will crash and throw an
exception when talking to v2 frontends.
Merge branch 'master_3614'