osdep: Retry SETLK upon EINTR

We could hit lock failure if there is a signal that makes fcntl return
-1 and errno set to EINTR. In this case we should retry.

Cc: qemu-stable@nongnu.org
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit f86428a1f4)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

util/osdep.c

@@ -244,7 +244,9 @@ static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
         .l_type   = fl_type,
     };
     qemu_probe_lock_ops();
-    ret = fcntl(fd, fcntl_op_setlk, &fl);
+    do {
+        ret = fcntl(fd, fcntl_op_setlk, &fl);
+    } while (ret == -1 && errno == EINTR);
     return ret == -1 ? -errno : 0;
 }