cli-command : Fix wrong condition check of pa_module_load

pa_module_load API's return value is integer which is enum pa_error_code_t with minus such as -PA_ERR_IO if the module loading is failed. pa_cli_command_load gets a return value of pa_module_load as pa_error_code_t which is wrong. Minus integer value could not covert to enum which is defined equal or larger than 0 so that pa_cli_command_load would recognize the return value as larger than 0 if pa_module_load return value (integer) is minus.

To fix this issue, I modified return value check logic of pa_module_load API. As same as pa_module_load's return type, integer would be used to check if module load is failed in pa_cli_command_load and the return value would be compared with minus.

Fixes: #3801 (closed)