net: ip: shell: Fix ipv4 echo reply callback to unref packet
net: ip: shell: Fix ipv4 echo reply callback to unref packet

The ICMPv4 handler needs to unref the received echo reply packet
because we are returning NET_OK to caller. Similar change was done
for IPv6 earlier.

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

GiulianoFranchetto/zephyr,nashif/zephyr,galak/zephyr,mbolivar/zephyr,zephyriot/zephyr,explora26/zephyr,ldts/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr,explora26/zephyr,explora26/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,punitvara/zephyr,zephyriot/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,finikorg/zephyr,zephyriot/zephyr,Vudentz/zephyr,finikorg/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,nashif/zephyr,ldts/zephyr,nashif/zephyr,explora26/zephyr,mbolivar/zephyr,kraj/zephyr,explora26/zephyr,galak/zephyr,galak/zephyr,zephyriot/zephyr,galak/zephyr,kraj/zephyr,mbolivar/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,punitvara/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,punitvara/zephyr,zephyriot/zephyr,kraj/zephyr,finikorg/zephyr,kraj/zephyr