strongswan: merging the swanctl and strongswan configurations block by block

strongswan: merging the swanctl and strongswan configurations block by block

In the 'prepare_env' function, the configuration setup for 'swanctl' and
'strongswan' is not grouped into blocks, so it is not clear which functions
depend on each other.

With this change, the 'strongswan' configuration is set up first,
followed by the 'swanctl' configuration.

This commit does not change the function and is a preparatory commit.

Signed-off-by: Florian Eckert <redacted>