(GH-826) SYSTEM user always uses machine TEMP

Using `Path.GetTempPath()` instead of
`Environment.GetEnvironmentVariable("TEMP")` in 76ae7e2 for GH-532
has caused the SYSTEM user to return one of the following:

 * `c:\windows\system32\config\systemprofile\appdata\local\temp`
 * `c:\windows\syswow64\config\systemprofile\appdata\local\temp`

These folders seem to cause issues with accessing files, causing all
kinds of fun issues, such as "Not able to read package from path" and
not able to find executables being downloaded to these folders.

If one of these two folders is detected, ensure that the folder
structure is `%SystemRoot%\TEMP`.

src/chocolatey/infrastructure.app/ApplicationParameters.cs

@@ -76,6 +76,8 @@ public static class Environment
             public static readonly string Path = "Path";
             public static readonly string PathExtensions = "PATHEXT";
             public static readonly string PsModulePath = "PSModulePath";
+            public static readonly string Temp = "TEMP";
+            public static readonly string SystemUserName = "SYSTEM";
             public static readonly string Username = "USERNAME";
             public static readonly string ProcessorArchitecture = "PROCESSOR_ARCHITECTURE";
             public static readonly string EnvironmentSeparator = ";";

src/chocolatey/infrastructure/filesystem/DotNetFileSystem.cs

@@ -94,7 +94,14 @@ public string get_full_path(string path)
 
         public string get_temp_path()
         {
-            return Path.GetTempPath();
+            var path = Path.GetTempPath();
+
+            if (System.Environment.UserName.contains(ApplicationParameters.Environment.SystemUserName) || path.contains("config\\systemprofile\\appdata"))
+            { 
+                path = System.Environment.ExpandEnvironmentVariables(System.Environment.GetEnvironmentVariable(ApplicationParameters.Environment.Temp, EnvironmentVariableTarget.Machine).to_string());
+            }
+
+            return path;
         }
 
         public char get_path_directory_separator_char()