ShellPkg: Correct 3 places where memory was not being properly released by the shell.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Erik Bjorge <erik.c.bjorge@intel.com>
Reviewed-by: Liu, Jiang A <jiang.a.liu@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13938 6f19259b-4bc3-4df7-8a09-765794883524

ShellPkg/Application/Shell/ShellEnvVar.c

@@ -105,7 +105,7 @@ FreeEnvironmentVariableList(
   }
 
   for ( Node = (ENV_VAR_LIST*)GetFirstNode(List)
-      ; IsListEmpty(List)
+      ; !IsListEmpty(List)
       ; Node = (ENV_VAR_LIST*)GetFirstNode(List)
      ){
     ASSERT(Node != NULL);