Add SABAYON_UPGRADE_REPO env

* the argument of the inner_chroot_script.sh is not used anymore.
  For set sabayon-limbo repository we need set SABAYON_UPGRADE_REPO
  variable with value sabayon-limbo.

* equo upgrade is done only one time if SABAYON_UPGRADE_REPO is set.

scripts/inner_chroot_script.sh

@@ -1,7 +1,5 @@
 #!/bin/bash
 
-UPGRADE_REPO="${1}"
-
 /usr/sbin/env-update
 . /etc/profile
 
@@ -66,17 +64,6 @@ rm -f /etc/env.d/02locale
 ln -sf ../locale.conf /etc/env.d/02locale
 
 
-if [ -n "${UPGRADE_REPO}" ]; then
-	echo "Upgrading system by enabling ${UPGRADE_REPO}"
-	equo repo enable "${UPGRADE_REPO}" || exit 1
-	FORCE_EAPI=2 safe_run equo update || exit 1
-
-	equo repo mirrorsort "${UPGRADE_REPO}"  # ignore errors
-	ETP_NONINTERACTIVE=1 safe_run equo upgrade --fetch || exit 1
-	ETP_NONINTERACTIVE=1 equo upgrade --purge || exit 1
-	echo "-5" | equo conf update
-fi
-
 # Cleanup Perl cruft
 perl-cleaner --ph-clean