dump: initilize vmas in the very beginning

When dump/pre-dump failed before initializing vmas, free_mappings(&vmas)
is called and this cause segfault. Lets initialize vmas in the very
beginning of dump.
Signed-off-by: Ruslan Kuprieiev <kurpuser@gmail.com>

seqfault.patch
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -1296,6 +1296,9 @@ static int pre_dump_one_task(struct pstree_item *item, struct list_head *ctls)
 	int ret = -1;
 	struct parasite_dump_misc misc;
 
+	INIT_LIST_HEAD(&vmas.h);
+	vmas.nr = 0;
+
 	pr_info("========================================\n");
 	pr_info("Pre-dumping task (pid: %d)\n", pid);
 	pr_info("========================================\n");
@@ -1359,6 +1362,9 @@ static int dump_one_task(struct pstree_item *item)
 	struct proc_posix_timers_stat proc_args;
 	struct proc_status_creds cr;
 
+	INIT_LIST_HEAD(&vmas.h);
+	vmas.nr = 0;
+
 	pr_info("========================================\n");
 	pr_info("Dumping task (pid: %d)\n", pid);
 	pr_info("========================================\n");