Add trivial test case to make sure shared-cache mode does not automatically turn on exclusive-locking mode.

FossilOrigin-Name: a0ab3902f1431c962a5d034647ef3c6876dc0e75

test/lock_common.tcl

@@ -58,6 +58,7 @@ proc do_multiclient_test {varname script} {
     code3 { db3 close }
     catch { close $::code2_chan }
     catch { close $::code3_chan }
+    catch { db close }
   }
 }