Make "autosign" system test work with BusyBox awk

The BusyBox version of awk treats some variables which other awk
implementations consider to be decimal values as octal values.  This
intermittently breaks key event interval calculations in the "autosign"
system test, trigger false positives for it.  Prevent the problem from
happening by stripping leading zeros from the affected awk variables.

(cherry picked from commit ad008f7dbf)

bin/tests/system/autosign/tests.sh

@@ -1168,7 +1168,7 @@ status=`expr $status + $ret`
 # event scheduled is within 10 seconds of expected interval.
 check_interval () {
         awk '/next key event/ {print $2 ":" $9}' $1/named.run |
-	sed 's/\.//g' |
+	sed -e 's/\.//g' -e 's/:0\{1,4\}/:/g' |
             awk -F: '
                      {
                        x = ($6+ $5*60000 + $4*3600000) - ($3+ $2*60000 + $1*3600000);