Add unknown reason as stack for unknown patterns

I think inspect bug was expecting a stack to be present so just set it as
unkown.

Bug: 24304795
Change-Id: Ia91246f2769889e7bb11bd2b8b972d8a92afc0ef

src/com/android/loganalysis/parser/KernelLogParser.java

@@ -176,6 +176,7 @@ public class KernelLogParser implements IParser {
             unknownReset.setEventTime(mStopTime);
             unknownReset.setPreamble(mPreambleUtil.getLastTail());
             unknownReset.setCategory(KERNEL_RESET);
+            unknownReset.setStack("Unknown reason");
             mKernelLog.addEvent(unknownReset);
         }
     }

tests/src/com/android/loganalysis/parser/KernelLogParserTest.java

@@ -114,6 +114,7 @@ public class KernelLogParserTest extends TestCase {
         MiscKernelLogItem item = kernelLog.getMiscEvents(KernelLogParser.KERNEL_RESET).get(0);
         assertEquals(2.0, item.getEventTime(), 0.0000005);
         assertEquals("[    0.000000] Start\n[    2.000000] End", item.getPreamble());
+        assertNotNull(item.getStack());
     }
 
     public void testParseKnownGoodLastMessage() {