Fix platform_family recognition for centos/rhel based os

Change-Id: Ib2613b6cbbb68dc24caab36fff641c1b14e1074f
diff --git a/bootstrap.sh b/bootstrap.sh
index fe000df..a7f60bb 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -90,7 +90,7 @@
 elif [ "$FORMULAS_SOURCE" == "pkg" ]; then
   SALT_ENV=${SALT_ENV:-prd}
 fi
-eval $(cat /etc/*release 2> /dev/null)
+eval "$(grep -h '=' /etc/*release 2> /dev/null)"
 PLATFORM_FAMILY=$(echo ${ID_LIKE// */} | tr A-Z a-z)
 case $PLATFORM_FAMILY in
   debian )