Issue warning if reboot needed but exit with success

[ehelms]

When a reboot is required we want to bring attention to it via a warning but we do not want to fail the upgrade. This introduces a new option to issue a informational warning that still exits 0.

[ehelms]

Results in the following output:

================================================================================
Clean old Kernel and initramfs files from tftp-boot:                  [OK]
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Check number of fact names in database:                               [OK]
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Check whether all services are running:                               [OK]
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Check whether all services are running using the ping call:           [OK]
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Check for paused tasks:                                               [OK]
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Check whether system is self-registered or not:                       [OK]
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Check if system needs reboot:                                         [WARNING]
Updating Subscription Management repositories.
Core libraries or services have been updated since boot-up:
  * dbus
  * dbus-daemon
  * glibc
  * kernel
  * linux-firmware
  * systemd
  * zlib (dependency of dbus. Recommending reboot of dbus)

Reboot is required to fully utilize these updates.
More information: https://access.redhat.com/solutions/27943
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Upgrade finished.
[root@ ~]# $?
-bash: 0: command not found