host-dump: Renamed host-dump-offload-transport build option

Currently dump manager using "host-dump-offload-transport" to mention
the transport protocol name to offload host dumps but, same transport
can use to other actions i.e create and delete. So, Changing build option
name into "host-transport" to make generic.

Also, transport code sources files are organized based on "offload" name
so, changed same as "host-transport".

Signed-off-by: Ramesh Iyyar <rameshi1@in.ibm.com>
Change-Id: I9e229218ea8c606e7092daf4d24fd6d16eb425c8