Replace fgrep and egrep with grep -F/-E

GNU Grep 3.8 reports the following warnings:

    egrep: warning: egrep is obsolescent; using grep -E
    fgrep: warning: fgrep is obsolescent; using grep -F

bin/tests/system/dlzexternal/tests.sh

@@ -45,7 +45,7 @@ EOF
 	return 1
     }
 
-    out=`$DIG $DIGOPTS -t $type -q $host | egrep "^$host"`
+    out=`$DIG $DIGOPTS -t $type -q $host | grep -E "^$host"`
     lines=`echo "$out" | grep "$digout" | wc -l`
     [ $lines -eq 1 ] || {
 	[ "$should_fail" ] || \