Fuzztest: run whole corpus for non-embedded targets.

This is a tradeoff between test time and test coverage.
After consideration, I've decided it is better to catch
potential problems earlier even though it increases test
time by ~15 seconds.
diff --git a/tests/fuzztest/SConscript b/tests/fuzztest/SConscript
index 132744e..7c0d6e2 100644
--- a/tests/fuzztest/SConscript
+++ b/tests/fuzztest/SConscript
@@ -85,8 +85,10 @@
 
     if env.has_key("FUZZTEST_CORPUS_SAMPLESIZE"):
         samplesize = int(env["FUZZTEST_CORPUS_SAMPLESIZE"])
-    else:
+    elif env.has_key("EMBEDDED"):
         samplesize = 100
+    else:
+        samplesize = 4096
 
     files = [n for n in corpus.namelist() if not n.endswith('/')]
     files = random.sample(files, min(samplesize, len(files)))