[BZ 1015334] EAP 6 host controller domain host update results in managed
servers no longer being "manageable"

This commit deprecates 'domainHost' read-only pluginConfiguration property.
Instead new trait called 'Domain Host Name' was introduced.
BaseServerComponent#validateServerAttributes() now also checks for HC name
and if needed re-reads it from host.xml file. When <host name= changes,
deprecated 'domainHost' property does not get updated (since there is no way
from plugin avail code to update pluginConfiguration on server).
BaseServerComponent now handles 'domainHost' in memory, this variable gets
updated on component start or in avail code (when server was DOWN and now is
UP). Managed servers have domain host name as part of resource key, they get
correctly discovered when this change occurs.
[BZ 1015334] EAP 6 host controller domain host update results in managed
servers no longer being "manageable"

Fixed javadocs, renamed variables. Also made access to ASHostName
synchronized since it's value can be changed from avail thread and is being
read all over other threads. Big change of this commit is getAvailability().
Now we directly read server's name attribute instead of 'launch-type' (which
was probably lets-just-read-something) and in case of failure (making we
just failed to read value, but connection and other stuf is OK) we re'read
<host name from file and try the request again. This approach is more robust
than previous, which was only able to detect the change in case server avail
went from DOWN to UP. Now, we can detect the change anytime.
Merge pull request #23 from lzoubek/bugs/1015334

[BZ 1015334] EAP 6 host controller domain host update results in managed servers no longer being "manageable"