add X509_USER_PROXY to the variables propagated to the LbEnv environment
New features: add X509_USER_PROXY to the variables propagated to the LbEnv environment
Fixes:
Improvements: the Dirac proxy path is propagated to the LbEnv environment in case the user has set a custom path
Internal changes: add X509_USER_PROXY to vars
when LbEnv is started