MDEV-30236 set TaskMax=99% in the MariaDB systemd unit

Originally requested to be infinity, but rolled back to 99%
to allow for a remote ssh connection or the odd needed system
job. This is up from 15% which is the effective default of
DefaultTasksMax.

Thanks Rick Pizzi for the bug report.

support-files/mariadb.service.in

@@ -140,6 +140,12 @@ PrivateTmp=false
 TimeoutStartSec=900
 TimeoutStopSec=900
 
+# Set the maximium number of tasks (threads) to 99% of what the system can
+# handle as set by the kernel, reserve the 1% for a remote ssh connection,
+# some monitoring, or that backup cron job. Without the directive this would
+# be 15% (see DefaultTasksMax in systemd man pages).
+TasksMax=99%
+
 ##
 ## Options previously available to be set via [mysqld_safe]
 ## that now needs to be set by systemd config files as mysqld_safe

support-files/mariadb@.service.in

@@ -252,6 +252,12 @@ PrivateTmp=false
 TimeoutStartSec=900
 TimeoutStopSec=900
 
+# Set the maximium number of tasks (threads) to 99% of what the system can
+# handle as set by the kernel, reserve the 1% for a remote ssh connection,
+# some monitoring, or that backup cron job. Without the directive this would
+# be 15% (see DefaultTasksMax in systemd man pages).
+TasksMax=99%
+
 # Controlling how multiple instances are separated. See top of this file.
 # Note: This service isn't User=mysql by default so we need to be explicit.
 # It is as an option here as a user may want to use the MYSQLD_MULTI_INSTANCE