Make 'no_timer_check' Kernel parameter for Fedora cloud images

[Kashyap Chamarthy]

Heya,

This is a brief summary of discussions re `no_timer_check` Kernel
parameter from different bug trackers (see references below for more
details) 


What?
-----

Make 'no_timer_check' Kernel parameter default for Fedora cloud images.


Why?
----

It has been reported (recently and in the past) many times[1][2][3] that
Kernel timer checks are not reliable/helpful in the context of
virtualization and it's useful to disable

This is also useful to elimiate false-positives in upstream
OpenStack CI testing[1][2].


Notes
-----

  - 'no_timer_check' parameter is added implicitly when the kernel
    detects it is booting under KVM.

    However when booting under QEMU TCG (software emulation) you have to
    add this to the guest kernel command line explicitly.

    (Thanks Richard WM Jones.)


  - About 'no_timer_check', from Kernel documentation[4]:

        'no_timer_check'  [X86,APIC] Disables the code which tests for
                          broken timer IRQ sources. 


References
----------

 [1] https://bugs.launchpad.net/cirros/+bug/1312199 -- cirros 0.3.1
     fails to boot 
       - Relevant comments: #1, #2, and #4

 [2] https://bugzilla.redhat.com/show_bug.cgi?id=1102592 -- F20 could
     image affected by timing issues when using with soft-qemu

 [3] https://bugzilla.redhat.com/show_bug.cgi?id=502058#c15 -- qemu
     -no-kvm guest hangs at during timer setup; works with noapic

 [4] https://www.kernel.org/doc/Documentation/kernel-parameters.txt


-- 
/kashyap