During text mode installation, No error checking available for the screens "Domain name", "name server" and "HTTP Proxy" configuration

[Michael Hohnbaum]

Bug oriignally reported by Manvanthara Puttashankar

Host details:
Platform: PPC64LE
[root@localhost ~]# uname -a
Linux localhost 3.10.23-900.pkvm2_1.1.ppc64 #1 SMP Wed Feb 5 02:46:25 CST 2014 ppc64 ppc64 ppc64 GNU/Linux
[root@localhost ~]# cat /etc/issue
IBM PowerKVM release 2.1 build 9 Beta (pkvm2_1)
Kernel \r on a \m (\l)

Ubuntu details:
Daily Build: Ubuntu 14.04 Alpha2 feb28

Summary: During text mode installation, No error checking available for the screens "Domain name",
"name server" and "HTTP Proxy" configuration.

Steps to reproduce:
1. [root@localhost manu]# qemu-img create -f qcow2 ubuntu_alpha3_M1.qcow2 80G
Formatting 'ubuntu_alpha3_M1.qcow2', fmt=qcow2 size=85899345920 encryption=off cluster_size=65536 lazy_refcounts=off

2.[root@localhost manu]# virt-install --name=manu1_alpha3 --ram 2048 --cdrom /var/lib/libvirt/images/Alpha_ISO/trusty-server-ppc64el.iso --disk path=/var/lib/libvirt/images/manu/ubuntu_alpha3_M1.qcow2,bus=virtio,size=10,format=qcow2,cache=none --bridge=virbr0 --mac=52:54:02:70:75:6C

3. During the installation,
   a. under Domain name configuration, if you enter invalid value "(*&". There is no appropriate error checking invalid entry
   b. under Name server addresses configuration, If the value entered is "192.168.122.1,192.168.122.1, 192.168.122.1" there is no appropriate error checking.
   c. under HTTP Proxy configuration, If the value entered is "-)324. hfduj*", there is no appropriate error checking.

Expected Behavior: "domain name", "name server" and "HTTP Proxy" screen should have appropriate error checking mechanism.