ppc64 grub2: Fix the location for creating grub2 config files

Bug: 1144106
Change-Id: Iea8aab6702dabd1d41ea32f8440dd06aa7f7937e
better usage message for bkr job-cancel

Bug: 867561
Change-Id: I0651ab1cb646bcb3dfa2cd9e7af4029962f9015a
skip non-existent repos when importing .composeinfo

Bug: 1140995
Change-Id: I43ce928605cdb7b18d96b3ef40ec75db9cc8f5af
use absolute TFTP paths in GRUB2 configs

GRUB2 just uses the filenames literally as they are given in the config
file, it doesn't resolve them relative to the config path or anything.
So currently it is sending TFTP requests for paths like:

    ../images/system.example.com/kernel

As it happens, the TFTP server just strips off the initial .. and
honours the request, which is why it has always seemed to work. But
really it should just be requesting an absolute TFTP path starting
/images/.

Change-Id: Ic98be66af49aac21a428353538c10305ead36d86
also set tags from .composeinfo label

Bug: 1140999
Change-Id: I75b6baa095bdfdcef9199ee7a5b4a72ed175a172
ppc64 grub2: workarounds to work around grub2/power8 incosistencies

Bug: 1144106
Change-Id: I25517f9ec43336917e673065fe581aa1615f4c25
remove extra serial console parameters from guest kickstarts

Bug: 1148943
Change-Id: I5aec66e1f1365845b919ab9135ca8c673486bb41
release notes for 0.18.2

Change-Id: I303dab1f921cd4e6bd46d49f78f5edf67dd7c621
Automatic commit of release 0.18.2