jjb: Add older LTS kernel versions

lttng-modules stable-2.13 supports Linux >= 3.0 at this time. When
`dev_review_` jobs for this branch are run, the version ranges are set
with `kverceil` and `kverfloor`, then filtered according to
`lts-head`. Since only more recent LTS kernels were added to
`lts_kversions`, CI tests weren't running against as wide of a range
of kernels as suggested by the project's support matrix.

Change-Id: Id49eca88732ed2cdd840e717e13c9161b35f2e81
Signed-off-by: Kienan Stewart <kstewart@efficios.com>