Escape source dataset name when mapping to destination path in znapzendztatz

The substitution that derives the destination dataset path interpolated
$backupSet->{src} into a regex without quotemeta. ZFS dataset names may
contain '.', which then matches any character, so the wrong prefix could be
rewritten and statistics shown for the wrong destination. Wrap the source in
\Q...\E, matching the already-correct form in ZnapZend.pm.

Author: moetiker

bin/znapzendztatz

@@ -139,7 +139,7 @@ sub main {
                 }
                 else{
                     my $dstDataSet = $dataset;
-                    $dstDataSet =~ s/^$backupSet->{src}/$backupSet->{$key}/;
+                    $dstDataSet =~ s/^\Q$backupSet->{src}\E/$backupSet->{$key}/;
                     dumpStats(collectData($backupSet->{src}, $key, $dstDataSet, $snapFilter), $opts->{H}, $opts->{setup});
                 }
             }