Fix: memory and fd leaks in error counter

Use a regular pattern for all commands:

If the command callback takes ownership of a pointer or file descriptor,
it sets them to NULL or -1. Therefore, the caller can always try to free
the pointer, or close it if it is greater or equal to 0.

This eliminates memory and fd leaks on error.

Change-Id: I4916920095526c166636c6a432b95fdd6fd1ca4b
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>