ENG-7267 In sqlcmd, restore/complete errors returning to prompt (set m_interactive)
ENG-7267 SQLCMD backed out some recent over-engineering
Fix validation logic for handling null literal as parameter to stored
proc invoked via EXEC in sqlcmd.
Squashed commit of the following: Take final fix of Joinining hiding.
commit 29309c550e20832c56703d87a8005a0b4018676c
    Merge remote-tracking branch 'upstream/release-4.9.x' into release-4.9.x
    Added code to hide joining count from cluster health.
commit 6fb781844ad50ed6bcd4ebb253f329442188019d
    Removed Joining cluster
commit aedca65d88f366240b9b81de64f919819adb69c1
Merge pull request #1824 from VoltDB/ENG-7266-sqlcmd-exec-with-null-param

Fix validation logic for handling null literal as parameter to stored proc via sqlcmd
Merge pull request #1826 from VoltDB/ENG-7267-sqcmd-error-to-prompt

Eng 7267 sqcmd error to prompt
Update documentation PDFs in master
(cherry picked from commit 7785e110d6bb337c883997babb683516e3578a4a)
Minor update to doc PDFs.
Merge remote-tracking branch 'upstream/release-4.9.x' into release-4.9.x