t: cover improper kvs eventlogs

Problem: The flux kvs eventlog commands don't have coverage for
improperly formatted eventlogs.

Add some coverage to t1008-kvs-eventlog.t.

t/t1008-kvs-eventlog.t

@@ -224,6 +224,12 @@ test_expect_success 'flux kvs eventlog get fails on bad input' '
 	test_must_fail flux kvs eventlog get
 '
 
+test_expect_success 'flux kvs eventlog get fails on not an eventlog' '
+	flux kvs put test.noteventlog=foo &&
+	test_must_fail flux kvs eventlog get test.noteventlog 2> noteventlog1.err &&
+	grep "cannot decode" noteventlog1.err
+'
+
 test_expect_success 'flux kvs eventlog append fails on bad input' '
 	test_must_fail flux kvs eventlog append
 '
@@ -236,6 +242,11 @@ test_expect_success 'flux kvs eventlog wait-event fails on bad input' '
 	test_must_fail flux kvs eventlog wait-event
 '
 
+test_expect_success 'flux kvs eventlog wait-event fails on not an eventlog' '
+	test_must_fail flux kvs eventlog wait-event test.noteventlog foo 2> noteventlog2.err &&
+	grep "cannot decode" noteventlog2.err
+'
+
 #
 # ensure no lingering pending requests
 #