Support file extension in the RABBITMQ_CONFIG_FILE env var values

[hairyhum]

Fixes #691

[michaelklishin]

This breaks support for paths without a filename extension. The problematic line seems to be
the one with "${RABBITMQ_CONFIG_FILE%.*}":

export RABBITMQ_CONFIG_FILE=./etc/rabbitmq/rabbitmq
echo "${RABBITMQ_CONFIG_FILE%.*}"

export RABBITMQ_CONFIG_FILE=./etc/rabbitmq/rabbitmq.config
echo "${RABBITMQ_CONFIG_FILE%.*}"
./etc/rabbitmq/rabbitmq
export RABBITMQ_CONFIG_FILE=./etc/rabbitmq/rabbitmq.sysctl
echo "${RABBITMQ_CONFIG_FILE%.*}"
./etc/rabbitmq/rabbitmq
export RABBITMQ_CONFIG_FILE=./etc/rabbitmq/rabbitmq.sysctl.conf
echo "${RABBITMQ_CONFIG_FILE%.*}"
./etc/rabbitmq/rabbitmq.sysctl

[michaelklishin]

I've pushed something that fixes this particular problem by using dirname and basename. I'm hardly great at shell script, so @hairyhum and @dumbbell, please double check.

We also need to work on supporting both advanced and advanced.config.

[hairyhum]

Or we can just change conditions, because extension is being checked there anyway. So we can use any extension trimming mechanism.

[michaelklishin]

@hairyhum this passes the acceptance criteria for rabbitmq.conf and rabbitmq.config but not advanced.config. I think we should support both options for the advanced.config as well.

[hairyhum]

Added support for advanced.config. Haven't checked windows scripts yet.

[michaelklishin]

This looks good on OS X (zsh) and Ubuntu (dash). Haven't had a chance to test on Windows yet.

[Gsantomaggio]

this else if should be else if exist "!RABBITMQ_CONFIG_FILE!.conf" as rabbitmq-server.bat