[SPARK-5286][SQL] Fail to drop an invalid table when using the data source API

[yhuai]

JIRA: https://issues.apache.org/jira/browse/SPARK-5286

[SparkQA]

Test build #25677 has started for PR 4076 at commit 6b69ed1.

• This patch merges cleanly.

[SparkQA]

Test build #25677 has finished for PR 4076 at commit 6b69ed1.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[AmplabJenkins]

Test PASSed.
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https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/25677/
Test PASSed.

[marmbrus]

Thanks! Merging to master.