parasite: Code grouping in parasite_infect_seized
parasite: Code grouping in parasite_infect_seized

 - mmap_seized returns only NULL on error, drop
   redumdant test
 - setup control block in one group
 - no need for err_free label, xfree handles NULL easily
 - prepare registers for munmap_seized call on error path

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Acked-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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