fixed code to increase the port number because when exists more than one Slave Instances one varnish configuration uses the same port used in stunnel configuration. With this, one exception is raised

Varnish uses c-compiler to run. The gcc is used to compile the vcl script. With is needed pass the cc_command to compile the script and the commands "ld" and "as" are provided by binutils.
So, this change is to setup the PATH environment and pass the gcc binary to varnish command

If the cache is enabled, the varnish and stunnel will be added between frontend and backend. With this, the connection will be: frontend > varnish > stunnel > backend.

Move Slave Instance out of installFrontendApache implementation