Fix log checking in PRH so that only entries generated during test execution are taken into account.

- fixing "Should not send PNF ready when DMaaP event is not JSON array" test that was passing due to checking log entry generated by a previous test
- improving logs generated by keyword waiting for log entry
- changing 'find log entry' to 'wait for log entry' with explicit timeout setting
- adjusting timeouts for waiting for log entries to appear (20s is enough when prh workflow execution is scheduled every 10s)

Change-Id: I20c67dfce6e8d1809d24ddb3108a088b00165996
Issue-ID: DCAEGEN2-1544
Signed-off-by: grabinsk <maciej.grabinski@nokia.com>
diff --git a/tests/dcaegen2/prh-testcases/assets/ves-event-not-a-json-object/invalid-ves-event.json b/tests/dcaegen2/prh-testcases/assets/ves-event-not-a-json-object/invalid-ves-event.json
new file mode 100644
index 0000000..cf378eb
--- /dev/null
+++ b/tests/dcaegen2/prh-testcases/assets/ves-event-not-a-json-object/invalid-ves-event.json
@@ -0,0 +1 @@
+"notajsonobject"