execd_preinstall() is not executed in install hook

[Nobuto Murata]

exec.d/*/charm-pre-install was not executed in install hook. I needed to kick upgrade-charm to take effect of execd_preinstall().

[hooks/horizon_hooks.py]
@hooks.hook('install')
def install():
    configure_installation_source(config('openstack-origin'))
    apt_update(fatal=True)
    packages = PACKAGES[:]
    if os_release('openstack-dashboard') < 'icehouse':
        packages += ['nodejs', 'node-less']
    apt_install(filter_installed_packages(packages), fatal=True)

@hooks.hook('upgrade-charm')
@restart_on_change(restart_map())
def upgrade_charm():
    execd_preinstall()
    apt_install(filter_installed_packages(PACKAGES), fatal=True)
    CONFIGS.write_all()