fiber: Make sure the guard page is created

The mprotect() syscall may fail due to heavy memory
pressure (say there is no enough resources to split
VMAs and etc).

In this case we must not proceed without guard page
but refuse to create a new fiber.

Closes #4541

Signed-off-by: Kirill Yukhin <kyukhin@tarantool.org>
(cherry picked from commit e58dfe07189134297ea956eb70cd7d96e20a6c6e)