NPE during rebind (when memento file empty, perhaps?)

[aledsage]

The test FixedListMachineProvisioningLocationRebindTest.testRebindPreservesConfig() failed in buildhive:

https://buildhive.cloudbees.com/job/brooklyncentral/job/brooklyn/io.brooklyn$brooklyn-core/2150/testReport/junit/brooklyn.location.basic/FixedListMachineProvisioningLocationRebindTest/testRebindPreservesConfig/

Log output and exception is below. Two underlying problems:

1. Need to guard against a file in the persistence dir giving back a deserialized null - e.g. if it's empty.
2. The RebindTestUtils.waitForPersisted call in the test is supposed to wait for the file to be completely written so this should not have happened. If the file was being re-written then it will have been written to a temp location and then mv'ed across so we should never see an empty file.

2014-05-01 01:09:46,569 INFO TESTNG INVOKING CONFIGURATION: "Command line test" - @BeforeMethod brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.setUp()
2014-05-01 01:09:46,579 INFO Memento-persister will use directory /tmp/1398906586570-0
2014-05-01 01:09:46,674 INFO Started application Application[hdhOqiH6]
2014-05-01 01:09:46,895 INFO TESTNG PASSED CONFIGURATION: "Command line test" - @BeforeMethod brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.setUp() finished in 326 ms
2014-05-01 01:09:46,895 INFO TESTNG INVOKING: "Command line test" - brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.testRebindPreservesConfig()
2014-05-01 01:09:46,918 INFO Rebinding app, using directory /tmp/1398906586570-0
2014-05-01 01:09:46,923 INFO Memento-persister will use directory /tmp/1398906586570-0
2014-05-01 01:09:46,930 INFO Loading memento from /tmp/1398906586570-0; 1 entities, 3 locations, 0 policies
2014-05-01 01:09:47,024 WARN Problem during rebind (rethrowing)
java.lang.NullPointerException: null
at brooklyn.entity.rebind.dto.BrooklynMementoImpl$Builder.location(BrooklynMementoImpl.java:60) ~[classes/:na]
2014-05-01 01:09:47,026 INFO TESTNG FAILED: "Command line test" - brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.testRebindPreservesConfig() finished in 130 ms
java.lang.NullPointerException
at brooklyn.entity.rebind.dto.BrooklynMementoImpl$Builder.location(BrooklynMementoImpl.java:60)
at brooklyn.entity.rebind.persister.BrooklynMementoPersisterToMultiFile.loadMemento(BrooklynMementoPersisterToMultiFile.java:121)
at brooklyn.entity.rebind.RebindManagerImpl.rebind(RebindManagerImpl.java:213)
at brooklyn.entity.rebind.RebindTestUtils.rebind(RebindTestUtils.java:152)
at brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.rebind(FixedListMachineProvisioningLocationRebindTest.java:97)
at brooklyn.location.basic.FixedListMachineProvisioningLocationRebindTest.testRebindPreservesConfig(FixedListMachineProvisioningLocationRebindTest.java:61)
at org.apache.maven.surefire.testng.TestNGExecutor.run(TestNGExecutor.java:77)
at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.executeMulti(TestNGDirectoryTestSuite.java:189)
at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.execute(TestNGDirectoryTestSuite.java:105)
at org.apache.maven.surefire.testng.TestNGProvider.invoke(TestNGProvider.java:117)
at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray2(ReflectionUtils.java:208)
at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:158)
at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:86)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:95)

[aledsage]

Fix for NPE (point 1 above) in #1346