Remove symlink after `prepare storage` target

[alexvanin]

After #92 we have prepare.storage target that creates storage node's TLS certificate symlink to the host machine. However it never removed. make clean target removes storage node's certificate but it didn't affect symlink. It solves the issue technically, but it would be better if we will keep clean host machine.

Possible options:

• do not create symlink at prepare.storage target, but show ln -s command for the user to manage it on it's own (kinda like we propose to modify /etc/hosts file and do not modify it in the scripts,
• remove symlink at make clean target.

[fyrchik]

This may be related:

> make down clean >/dev/null 2>&1 && make up >/dev/null 2>&1 && ls -lh services/storage/s04tls*
-rw-r--r-- 1 dzeta dzeta 2,0K авг 23 16:31 services/storage/s04tls.crt
-rw------- 1 dzeta dzeta 3,2K авг 23 16:31 services/storage/s04tls.key

> make down clean up >/dev/null 2>&1 && ls -lh services/storage/s04tls*
services/storage/s04tls.crt:
итого 0

services/storage/s04tls.key:
итого 0
dzeta@wpc ~/r/neofs-dev-env (real-clean)>