Fixed typo's in few validation messages

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58683 65644016-39b1-43b1-bf79-96bc8fe82c15
Lets not return isc_att_shutdown error when some of the attachments in monitoring snapshot are gone while dump was creating

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58684 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed bug in downgrade()

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58685 65644016-39b1-43b1-bf79-96bc8fe82c15