scripts/suite.py: remove default -k (kernel) value

Note: will require current cron jobs to change to request -k testing
explicitly.  Removes current special meaning of '-k -'.

Fixes: #10304
Signed-off-by: Dan Mick <dan.mick@redhat.com>
Merge pull request #394 from ceph/wip-default-kernel

scripts/suite.py: change default kernel from 'testing' to '-'
Respect --os-version and --os-type in teuthology.run.

Remove default value of 'ubuntu' for --os-type for teuthology.run and
make sure that teuthology.misc.get_distro accounts for ctx.os_type now
defaulting to None instead of 'ubuntu'.

Signed-off-by: Andrew Schoen <aschoen@redhat.com>
moved the get_distro and get_distro_version functions from misc to provision as it was the only user of those functions

Signed-off-by: Andrew Schoen <aschoen@redhat.com>