*dcap, *ftp, ssh1: fix error handling

LoginManager is agnostic to the underlying protocol and delegates
this responsibility to some StreamEngine.  The StreamEngine is
instantated via reflection, which may result in an
InvocationTargetException being thrown, which wraps the underlying
cause of the problem.

There are two problems with the current code: first, if the underlying
problem is an Error (e.g. OutOfMemoryError) then this is not
propagated and dCache will try to continue in this ill-defined state;
second, the error message logged is that of the ITE, which does
not include a description of the underlying problem.

This patch fixes these two problems.

Target: master
Request: 2.6
Request: 2.2
Patch: http://rb.dcache.org/r/5906
Acked-by: Tigran Mkrtchyan
dcap: drop READV io log level from info to debug

Ticket: #7980
Acked-by: Paul Millar
Target: master, 2.6
Require-book: no
Require-notes: yes
IPv6: Improve address handling by Subnet (was 4639)

In some cases class Subnet handles converted IPv6 to IPv4 addresses in
an incorrect way: It accepts some invalid addresses and in some cases it
converts the address without adjusting the netmask.
This patch fixes these problems by adding special handling for special
addresses.

Acked-by: Tigran
Target: master
Require-book: no
Require-notes: no
gplazma-ldap: make DN search string configurable

added a new property to specify DN search criteria:

gplazma.ldap.userfilter

The default value is 'uid', which is used in posix
schema.

This is a very lite filter version. Can be changed if needed.

Acked-by: Paul Millar
Target: master,2.6
Require-book: yes
Require-notes: yes
Patch: http://rb.dcache.org/r/5922/
startup: fix logging multiple stacktraces on RuntimeException

When dCache fails to start up a service because a cell throws
a RuntimeException then the same stack-trace is logged three times:
once by AbstractCell's doInit and twice within Bootload.

This patch reduces this to just once.  It also fixes the problem
that multiple RuntimeExceptions have null as their message, so
toString is used instead.

Note that there is still a RuntimeException that wraps the previous
RuntimeException and adds the context information (which line and file
triggered the problem), therefore the stack-trace includes two
exceptions.

Target: master
Requires-book: no
Requires-notes: no
Patch: http://rb.dcache.org/r/5919
Acked-by: Tigran Mkrtchyan
poolmanager: provide reasonable error message if partition type is unknown

If the admin has saved a partition type 'classic' in their
poolmanager.conf then dCache will fail to start with a meaningless
error message and a stack-trace.

This patch provides a meaningful error message.  Due to a
hack/work-around for another problem, the message is wrapped in a
RuntimeException, which triggers reporting the problem as a bug (with
a stack-trace).

Target: master
Requires-notes: no
Requires-book: no
Patch: http://rb.dcache.org/r/5920/
Acked-by: Karsten Schwank