Avahi: Adding Asset interface in the script to generate unique hostname

xyz.openbmc_project.Inventory.Item.Bmc is a null
interface where the SerialNumber is not present.
xyz.openbmc_project.Inventory.Decorator.Asset
interface contains the SerialNumber and is replaced
in place of the former interface.

Tested by:

1. Finding SerialNumber in Inventory interface
   - busctl introspect xyz.openbmc_project.Inventory.Manager /xyz/openbmc_project/inventory/system/chassis/motherboard/boxelder/bmc

output:
   [[0;1;39mxyz.openbmc_project.Inventory.Decorator.Asset      [[0m interface -         -                  -
   .BuildDate                                          property  s         ""                 emits-change writable
   .Manufacturer                                       property  s         "IPS             " emits-change writable
   .Model                                              property  s         ""                 emits-change writable
   .PartNumber                                         property  s         "01DH137         " emits-change writable
   .SerialNumber                                       property  s         "YL10UF76W015    " emits-change writable

2. Finding hostname
   - hostname

output:
   witherspoon

(From meta-openpower rev: cb0591457e1af5e79e8ac63770897ec1f25a1d51)

Signed-off-by: asmithakarun <asmithkr@in.ibm.com>
Change-Id: Ia7234471503562cfcbe14630e2e1352a3a84062e
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-openpower/recipes-phosphor/network/first-boot-set-hostname/first-boot-set-hostname.sh b/meta-openpower/recipes-phosphor/network/first-boot-set-hostname/first-boot-set-hostname.sh
index cf67f8b..42a85b8 100644
--- a/meta-openpower/recipes-phosphor/network/first-boot-set-hostname/first-boot-set-hostname.sh
+++ b/meta-openpower/recipes-phosphor/network/first-boot-set-hostname/first-boot-set-hostname.sh
@@ -13,6 +13,7 @@
     MAPPER_PATH='/xyz/openbmc_project/object_mapper'
     INVENTORY_PATH='/xyz/openbmc_project/inventory'
     BMC_ITEM_IFACE='xyz.openbmc_project.Inventory.Item.Bmc'
+    INV_ASSET_IFACE='xyz.openbmc_project.Inventory.Decorator.Asset'
 
     BMC_ITEM_PATH=$(busctl --no-pager --verbose call \
                             ${MAPPER_IFACE} \
@@ -36,7 +37,7 @@
 
     BMC_SN=$(busctl get-property ${BMC_ITEM_SERVICE} \
                             ${BMC_ITEM_PATH} \
-                            ${BMC_ITEM_IFACE} SerialNumber)
+                            ${INV_ASSET_IFACE} SerialNumber)
     # 's "002B0DH1000"'
     BMC_SN=${BMC_SN#*\"}
     BMC_SN=${BMC_SN%\"*}