Adding /usr/sbin/ to PATH in adduser.sh for alpinelinux

s6 3.0.0.2 does not set PATH properly which makes
adduser not work. Setting it till future version
allows setting PATH.

Author: komailo

alpinelinux/root/etc/cont-init.d/01-adduser.sh

@@ -1,6 +1,7 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash
 
+export PATH=$PATH:/usr/sbin/ # s6 3.0.0.2 doesn't set PATH properly
 set -eu
 
 if [[ $EUID -ne 0 ]]; then