ZPool related memory leak fix

Close zpool_handle_t returned from zpool_iter, since they are opened
already by the function. This was leaking memory every time pools
were enumerated.

ZFSWrapper/ZFSNVList.cpp

@@ -281,6 +281,11 @@ namespace zfs
 	{
 	}
 
+	NVList::NVList(nvlist_t * list, TakeOwnership) :
+		m_list(list), m_ownsList(true)
+	{
+	}
+
 	NVList::~NVList()
 	{
 		reset();

ZFSWrapper/ZFSUtils.cpp

@@ -59,6 +59,8 @@ namespace zfs
 
 	ZPool::~ZPool()
 	{
+		if (m_handle)
+			zpool_close(m_handle);
 	}
 
 	ZPool::ZPool(ZPool && other) noexcept :

ZFSWrapper/ZFSUtils.hpp

@@ -51,6 +51,7 @@ namespace zfs
 	class ZPool
 	{
 	public:
+		// Takes ownership
 		explicit ZPool(zpool_handle_t * handle);
 		~ZPool();