Renamed containers->server_conatiners and refactored tests

[lkelly93]

• Moved /internal/container -> /internal/server_container
• Removed an auto failing test in executable_test.go

internal/server/server_container

• Added types_errors.go file, to hold all types for the package
  • Added UnreachableContainerError for when the container was created but can not be reached.
• Reworked the end of StartNewScheduler to check to see if it can connect to the container if it has been started. If it can't then it returns the new error mentioned above and the IP address for the container. If it can then it just returns the IP address.
• Changed tests for this package to create a scheduler during setup.