Fix running with DEBUGTEST
Fix running with DEBUGTEST

The fix is to remove the quotes around the optional_docker_run_args
variable expansion in the "docker run" command.  With quotes, when the
variable is undefined, the command is interpreted with an empty string
as an argument:
`docker run -t "" -v [...]`

Instead, we want the command to be interpreted as:
`docker run -t  -v [...]`

MichaelSimons/dotnet-docker,MichaelSimons/dotnet-docker,dotnet/dotnet-docker,dotnet/dotnet-docker