Add the "eForce" parameter to the sqlite3_multiplex_shutdown() entry point

in test_multiplex.c.  Shutdown is forced if true.  Shutdown is not done if
there are pending database connections and eForce is false, but an error log
entry is made instead.

FossilOrigin-Name: c7303d0139f7e7f4fa7060b52942e6c6c6d4b622

test/multiplex.test

@@ -68,6 +68,12 @@ proc multiplex_delete {name} {
 }
 
 db close
+sqlite3_shutdown
+test_sqlite3_log xLog
+proc xLog {error_code msg} {
+  lappend ::log $error_code $msg 
+}
+unset -nocomplain log
 
 multiplex_delete test.db
 multiplex_delete test2.db
@@ -188,12 +194,16 @@ do_test multiplex-2.3.1 {
 } {}
 
 
+unset -nocomplain ::log
 do_test multiplex-2.4.1 {
   sqlite3_multiplex_shutdown
 } {SQLITE_MISUSE}
 do_test multiplex-2.4.2 {
   execsql { INSERT INTO t1 VALUES(3, randomblob(1100)) }
 } {}
+do_test multiplex-2.4.3 {
+  set ::log
+} {SQLITE_MISUSE {sqlite3_multiplex_shutdown() called while database connections are still open}}
 do_test multiplex-2.4.4 { file size [multiplex_name test.x 0] } {7168}
 do_test multiplex-2.4.5 {
   db close