tests/rpm: always run ./autogen.sh to create missing files

In some occasions 'install-sh' seems to be missing in the 'make dist'
tarball when ./autogen.sh has not been run (skipped when 'configure'
exists). With this changes, 'autogen.sh' is always run so that missing
files should get added to the tarball.

Also write the logs from mock to a known location, and copy them to the
'/var/log/' directory that Jenkins archives after a regression test
failure. This makes it easier to find build issues that mock detects.

Change-Id: I8d0cf1afef61ebab0137aa0d20521e75a35ddbdd
BUG: 1038391
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/7786
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>