cleanup: Map test files according to structure in src

For example cmd_account() is located in src/command/cmd_funcs.c.
The unit test was located in tests/unittests/test_cmd_account.c.
Let's move it to a subdirectory like tests/unittests/command/test_cmd_account.c
to correpsond to the same structure.

tests/unittests/command/test_cmd_disconnect.c

@@ -0,0 +1,34 @@
+#include "prof_cmocka.h"
+#include <stdlib.h>
+#include <string.h>
+
+#include "xmpp/chat_session.h"
+#include "command/cmd_funcs.h"
+#include "xmpp/xmpp.h"
+#include "xmpp/roster_list.h"
+
+#include "ui/stub_ui.h"
+
+#define CMD_DISCONNECT "/disconnect"
+
+void
+clears_chat_sessions(void** state)
+{
+    chat_sessions_init();
+    roster_create();
+    chat_session_recipient_active("bob@server.org", "laptop", FALSE);
+    chat_session_recipient_active("mike@server.org", "work", FALSE);
+
+    will_return(connection_get_status, JABBER_CONNECTED);
+    will_return(connection_get_barejid, "myjid@myserver.com");
+    expect_any_cons_show();
+
+    gboolean result = cmd_disconnect(NULL, CMD_DISCONNECT, NULL);
+
+    assert_true(result);
+
+    ChatSession* session1 = chat_session_get("bob@server.org");
+    ChatSession* session2 = chat_session_get("mike@server.org");
+    assert_null(session1);
+    assert_null(session2);
+}