Apama Command Prompt should allow users to use their own SSL_CERT_FILE.

The apama_env script overwrote SSL_CERT_FILE in the environment. Users were unable to provide their own CA bundle to the Apama Command Prompt as SSL_CERT_FILE was overwritten with the default file shipped with Apama within the apama_env script. This issue is now resolved. The user can now set SSL_CERT_FILE in the environment and it will not be overwritten by apama_env.