Description:
SQL that use MDL (metadata locking) and "sleep" function, periodically
test a connection to see if it is alive. This functionality helps in
case of long lasting queries, where its essential to stop them because
they take resources like: Srv_session, memory, file descriptors etc.
This is already implemented for the classic-protocol.
For protocols that use the Command service (the xprotocol), the "connection_alive" check isn't performed and assumed to be true.

Approved by: Shivashankar Nagaraj <shiva.y.shankar@oracle.com>