Now fdinfos are collected independently from reg files and
sockets. During tihs collect we effectively create the mirroring
list of both by checking which type-IDs are added first.

Fix this by removing the fdinfo_desc and attaching fds directly
to collected reg files and sockets. Pipes and unix sockets will
be reworked in the same manner soon.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>