Rename NODEPOOL_CFG -> NODEPOOL_CFG_DIR

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Renames - add _DIR suffix

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Add variable NODEPOOL_CFG_BASENAME

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Move install script environment to python

Some of the environment variables will be re-used in the configuration
script.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
inp-nodepool-configure, inp-upload-keys

See README.md changes.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>