[enhancement]: render ds-identify through template renderer

[igalic]

Enhancement

right now, ds-identify is a static file, but has a lot environment variables:

PATH_ROOT=${PATH_ROOT:-""}
PATH_RUN=${PATH_RUN:-"${PATH_ROOT}/run"}
PATH_SYS_CLASS_DMI_ID=${PATH_SYS_CLASS_DMI_ID:-${PATH_ROOT}/sys/class/dmi/id}
PATH_SYS_HYPERVISOR=${PATH_SYS_HYPERVISOR:-${PATH_ROOT}/sys/hypervisor}
PATH_SYS_CLASS_BLOCK=${PATH_SYS_CLASS_BLOCK:-${PATH_ROOT}/sys/class/block}
PATH_DEV_DISK="${PATH_DEV_DISK:-${PATH_ROOT}/dev/disk}"
PATH_VAR_LIB_CLOUD="${PATH_VAR_LIB_CLOUD:-${PATH_ROOT}/var/lib/cloud}"
PATH_DI_CONFIG="${PATH_DI_CONFIG:-${PATH_ROOT}/etc/cloud/ds-identify.cfg}"
PATH_PROC_CMDLINE="${PATH_PROC_CMDLINE:-${PATH_ROOT}/proc/cmdline}"
PATH_PROC_1_CMDLINE="${PATH_PROC_1_CMDLINE:-${PATH_ROOT}/proc/1/cmdline}"
PATH_PROC_1_ENVIRON="${PATH_PROC_1_ENVIRON:-${PATH_ROOT}/proc/1/environ}"
PATH_PROC_UPTIME=${PATH_PROC_UPTIME:-${PATH_ROOT}/proc/uptime}
PATH_ETC_CLOUD="${PATH_ETC_CLOUD:-${PATH_ROOT}/etc/cloud}"
PATH_ETC_CI_CFG="${PATH_ETC_CI_CFG:-${PATH_ETC_CLOUD}/cloud.cfg}"
PATH_ETC_CI_CFG_D="${PATH_ETC_CI_CFG_D:-${PATH_ETC_CI_CFG}.d}"
PATH_RUN_CI="${PATH_RUN_CI:-${PATH_RUN}/cloud-init}"
PATH_RUN_CI_CFG=${PATH_RUN_CI_CFG:-${PATH_RUN_CI}/cloud.cfg}
PATH_RUN_DI_RESULT=${PATH_RUN_DI_RESULT:-${PATH_RUN_CI}/.ds-identify.result}

Ignoring the fact that lots of these are highly linux specific, others aren't trivially relocatable. While it's possible to override these with environment variables in the service starting ds-identify, it would be nice to not have to do that, and have the paths be correct on invocation of setup.py

[dch]

the underlying issue is that there needs to be a manual process to keep paths in the python sphere of cloudinit in sync with the shell script of ds-identify.

ideally there would be a single source of the truth.