improve initial console message

[phillxnet]

Thanks to forum user ericdude101 for highlighting this issue. Currently on first boot after install we have the following default console text (from /etc/issue):

Rockstor 3 (Core)
Kernel <version> on an x86_64

Rockstor login:

After a couple of minutes this message (via rockstor-core code) will be changed to the far more useful:

Rockstor is successfully installed.

You can access the web-ui by pointing your browser to https://<ip address>

or temporary and permanent network failure variants such as:

The system does not yet have an ip address.
Rockstor cannot be configured using the web interface without this.
Press Enter to receive updated network status
If this message persists please login as root and
configure your network using nmtui, then reboot.

However this delayed message update is not displayed until a carriage return (or several) are received.

This is very non intuitive and it is proposed that the initial message be changed to something like:

Please wait while Rockstor performs it's first boot initialisation.
Press Enter to receive updated status messages.
This process should take no longer than 4 minutes.

One approach to implement this change might be to add our desired message in an additional file:
ie /issue-first-boot
and have a ks.cfg %post entry akin to:

%post --nochroot
# establish our first boot after install console message
cp /issue-first-boot /mnt/sysimage/etc/issue
%end

reference: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Installation_Guide/s1-kickstart2-postinstallconfig.html

This approach has not been attempted by the author but may server as a starting point to the resolution of this issue in a relatively simply fashion.

Related functions in Rockstor's boot life cycle:
scripts/initrock.py - main() has a 1 minute (every 2 seconds) issue message update mechanism.
scripts/initrock.py - init_update_issue()
system/osi.py - update_issue(ipaddr)

Please update the following forum thread on this issue's resolution:
https://forum.rockstor.com/t/installation-problems/3096