Fix closing parasite fpage fd

Author: mkozlowski

parasite.c

@@ -33,7 +33,7 @@
 #define __stringify(x...)	__stringify_1(x)
 
 static int finish;
-static int fpage;
+static int fpage = -1;
 
 #define PAGEMAP_BUF_SIZE (4096/sizeof(uint64_t))
 static uint64_t pagemap_buf[PAGEMAP_BUF_SIZE];