vcl: try to disable font cache in CppUnit tests

With size 1 every ImplFontEntry should be immediately deleted, which
makes tools like valgrind and drmemory more useful.

Change-Id: Idec40c7cf7d927146f23830a42b3464c1675207f

vcl/source/outdev/font.cxx

@@ -1409,7 +1409,7 @@ void ImplFontCache::Acquire(ImplFontEntry* pEntry)
 
 void ImplFontCache::Release(ImplFontEntry* pEntry)
 {
-    static const int FONTCACHE_MAX = 50;
+    static const int FONTCACHE_MAX = getenv("LO_TESTNAME") ? 1 : 50;
 
     assert(pEntry->mnRefCount > 0 && "ImplFontCache::Release() - font refcount underflow");
     if( --pEntry->mnRefCount > 0 )