BufferQueueProducer: Log verbose log to warning instead of error.

Previously, this printed very verbose/spammy logs when there was
nothing actionable  users or developers could do to improve what
seemed like correct behavior to the user. Move this log to 'warning'
to still provide the information while reducing spam.


Bug: http://b/140581935
Change-Id: Iba5fc100a99594a7ac6df240b2468ffedfde249c