Fix Sysbench TPCC PopulateDatabase passing --warehouses 0 on small VMs (#675)

On VMs with 4 vCPUs or fewer, GetWarehouseCount returns 1, causing the
Populate mode calculation (warehouseEstimate - 1) to yield 0. This passes
--warehouses 0 to populate-database.py, which calls sysbench tpcc prepare
with --scale=0, dropping and recreating all tables with zero data. The
client then fails with nil value errors on every run attempt.

Fix: Use Math.Max(1, warehouseEstimate - 1) to ensure at least 1 warehouse
is always passed to the populate step.

Co-authored-by: Alex Williams-Ferreira <alexwill@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

src/VirtualClient/VirtualClient.Actions.UnitTests/Sysbench/SysbenchConfigurationTests.cs

@@ -276,7 +276,7 @@ public async Task SysbenchConfigurationProperlyExecutesTPCCPreparation()
 
             string[] expectedCommands =
             {
-                $"python3 {this.mockPackagePath}/populate-database.py --dbName sbtest --databaseSystem MySQL --benchmark TPCC --threadCount 8 --tableCount 10 --warehouses 0 --password [A-Za-z0-9+/=]+ --hostIpAddress \"1.2.3.5\""
+                $"python3 {this.mockPackagePath}/populate-database.py --dbName sbtest --databaseSystem MySQL --benchmark TPCC --threadCount 8 --tableCount 10 --warehouses 1 --password [A-Za-z0-9+/=]+ --hostIpAddress \"1.2.3.5\""
             };
 
             int commandNumber = 0;

src/VirtualClient/VirtualClient.Actions/Sysbench/SysbenchExecutor.cs

@@ -427,7 +427,7 @@ protected string BuildSysbenchLoggingArguments(SysbenchMode mode)
                     int warehouseCount = mode switch
                     {
                         SysbenchMode.Prepare => 1,
-                        SysbenchMode.Populate => warehouseEstimate - 1,
+                        SysbenchMode.Populate => Math.Max(1, warehouseEstimate - 1),
                         SysbenchMode.Run => warehouseEstimate,
                         _ => warehouseEstimate
                     };