frontend/pkgdeps: Add pylint and passwd

In order to make it easier to execute the checks required
for autotest regression, bring in pylint and passwd when
installing the dependent packages.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
install-autotest-server.sh: (Ubuntu) Make the autotest user use bash

Use bash instead of dash for the autotest user. It is
better and easier to get the automated regression going
than having to set a more unique PS1 prompt.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
install-autotest-server.sh: Fail when distro is not supported

If the distro is not supported, the script must exit
with return code != 0.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>