... which could help catch copy-paste errors when wrong guard is cleared
second time.

Also an assert added that when resetting, there's something to reset
(i.e., no descendant class had cleared protected pResetT, making reset
impossible, and thus actually unable to guard anything).

framework/source/layoutmanager/layoutmanager.cxx: made sure to not call
clear() second time

framework/source/layoutmanager/toolbarlayoutmanager.cxx: restored lock
lost in commit 777bc22c

forms/source/misc/InterfaceContainer.cxx: removed a leftover from commit
a19cd21e which reduced guarded scope

forms/source/component/DatabaseForm.cxx: fixed clear-reset sequence
broken from the initial commit bf4154eb

Change-Id: Ibab6660c79561eee31faf3e6c1128ab141a7e8a3
Reviewed-on: https://gerrit.libreoffice.org/70381
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>