Plug memory leaks on UNMAP and XCOPY with invalid parameters.

MFC after:	1 week
Do not pre-allocate reservation keys memory for every possible initiator.

In configurations with many ports, like iSCSI, each LUN is typically
accessed only by limited subset of ports.  Allocating that memory on
demand allows to reduce CTL memory usage from 5.3MB/LUN to 1.3MB/LUN.

MFC after:	1 month
Do not corrupt the listen string when parsing it.

This fixes problem with ctld reload when it is configured to listen on two
portals with same IP, but different ports.

MFC after:	1 week
Remove some unused code.