Code review comment for ~rodrigo-zaiden/ubuntu-cve-tracker:kernel_abi_check_cycle

I've added a new commit that changes the definition of the method
`get_kernel_sru_cycle` from kernel-abi-check script to kernel_lib.py.
In kernel-abi-check we call it from the kernel_lib.

It was suggested by Steve and it makes sense that the method is defined
in a common place where other scripts may take advantage of the method if
needed. for this case for example, we have the script 'kernel-sru-check'
that is placed in UQT nowadays but will be moved to UCT that could be using
it.

I'm passing the lp api connection as a parameter because we already have
it in kernel-abi-check. Another idea would be to have it also defined in
kernel_lib.py only if needed. I think python would not initialize another
instance if the connection was already initialized in kernel-abi-check,
but as I'm not sure, I preferred to keep it simpler.