i3: fix reloading for nixos module
i3: fix reloading for nixos module

By default, i3-msg gets socket from X11 property
which is not available when home manager is running
as nixos module.

This patch changes i3-msg command call by specifying
all i3 sockets found in $XDG_RUNTIME_DIR/i3 folder.

Fixes #252.

rycee/home-manager,rycee/home-manager,rycee/home-manager