modify linux ci to not test 1.xx tests. it cannot use language version 7.2 which is required for new Activity span types.

.vsts/linux-build.yml

@@ -21,25 +21,20 @@ steps:
     arguments: "--configuration Release"
 
 - task: DotNetCoreCLI@1
-  displayName: Test 2.0
+  displayName: Functional Tests 2.0
   continueOnError: true
   inputs:
     command: "test"
     projects: "test/**/*Tests20.csproj"
     arguments: "--configuration Release -l trx"
 
-- task: DotNetCoreInstaller@0
-  displayName: install dotnet core 1.1.5
-  inputs:
-    version: "1.1.5"
-
 - task: DotNetCoreCLI@1
-  displayName: Test 1.1.5
+  displayName: Unit Tests
   continueOnError: true
   inputs:
     command: "test"
-    projects: "test/**/*Tests.csproj"
-    arguments: "--configuration Release -l trx --filter Category!=WindowsOnly"
+    projects: "test/**/*AspNetCore.Tests.csproj"
+    arguments: "--configuration Release -l trx"
 
 
 - task: PublishTestResults@2
@@ -47,11 +42,6 @@ steps:
     testRunner: "VSTest"
     testResultsFiles: "**/*.trx"
 
-- task: DotNetCoreInstaller@0
-  displayName: install dotnet core 2.1.500
-  inputs:
-    version: "2.1.500"
-
 - task: DotNetCoreCLI@1
   displayName: Package Nuget
   inputs: