die early if db connection fails

scripts/zmupdate.pl.in

@@ -119,6 +119,9 @@ GetOptions(
     ) or pod2usage(-exitstatus => -1);
 
 my $dbh = zmDbConnect(undef, { mysql_multi_statements=>1 } );
+if ( !$dbh ) {
+  die "Unable to connect to db\n";
+}
 $Config{ZM_DB_USER} = $dbUser;
 $Config{ZM_DB_PASS} = $dbPass;
 # we escape dbpass with single quotes so that $ in the password has no effect, but dbpass could have a ' in it.