Fix return value or loglevel for several plugins

Fix return value or loglevel for several plugins

Some plugins' RC was != 0 and started to fail due to
stricter verification introduced by 3b9c7b2.
This commit fixes those return values.
For some plugins, fix verbosity of error message: non-zero rc
should be error, not warning.

Change-Id: I9a3f1f80e266858b6744fd9d9d99b352b8d94306

Change-Id: Ibf6ebc6cdc93c6e105d488e4a131dcb6e8eea19b

Change-Id: I35bac15fa0a89b068575739ac1cff0115c9d3a40

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Change-Id: I992002c56763fbdea5347e5b6e176cc86f5a08ce