Move solock() down to sosetopt(). A part of standalone sblock() work.

Move solock() down to sosetopt(). A part of standalone sblock() work.
This movement required because buffers related SO_SND* and SO_RCV*
socket options should be protected with sblock(). However, standalone
sblock() has different lock order with solock() and `so_snd' and
`so_rcv' buffers. At least sblock() for `so_snd' buffer will always be
taken before solock() in the sosend() path.

The (*pr_ctloutput)() call was removed from the SOL_SOCKET level 'else'
branch. Except the SO_RTABLE case where it handled in the special way,
this is null op call.

For SO_SND* and SO_RCV* cases solock() will be replaced by sblock() in
the future.

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