azure: Add JDK installed in vs2015 image to PATH

Add a JDK installed in vs2015 image to PATH, so java tests can be run

JDK appear to be installed in several places, so we can always pick a
different one:

C:\java\jdk\jdk1.8.0_102\bin\
C:\Program Files\Java\jdk1.8.0_102\bin
C:\Program Files (x86)\Java\jdk1.8.0_102\bin

ci/azure-steps.yml

@@ -43,12 +43,15 @@ steps:
        Set-Content "env:$p" "$v"
      }
 
-     # download and install python3 and add to path (since it's not installed in vs2015 image!)
      if ($env:compiler -eq 'msvc2015') {
+       # download and install python3 and add to path (since it's not installed in vs2015 image!)
        Set-ExecutionPolicy Bypass -Scope Process -Force
        iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))
        choco install python3 -y --no-progress --params "/InstallDir:C:\Python3"
        $env:Path = "C:\Python3;$env:Path"
+
+       # add JDK installed in vs2015 image to PATH
+       $env:Path = "C:\java\jdk\jdk1.8.0_102\bin\;$env:Path"
      }
 
      # test_find_program exercises some behaviour which relies on .py being in PATHEXT