CREATE TEMPORARY TABLE locks SE plugin 6 times. 5 of these locks are
released by the end of the statement. And only 1 acquired by
init_from_binary_frm_image() / plugin_lock() remains.
The lock removed in this patch was clearly redundant.
Part of MDEV-17805 - Remove InnoDB cache for temporary tables.
As it isn't used. This leaves a less clustered syntax
for a INSTALL IF EXISTS SONAME option which could be added later.
This option could be checking the existance of the soname rather than the
installed plugin name which the rest of the INSTALL IF NOT EXISTS
is focused around.`
Add INSTALL SONAME IF NOT EXISTS; syntax only, installing
duplicate SONAMES doesn't currently cause any errors or warnings.
UNINSTALL SONAME IF EXISTS was added.
Allow the installation / uninstallation of plugins without
doing checks for existence first.
