added string comparison to consumer m_restart_on_exception if statement

[datwiz]

The Kafka::Consumer@m_restart_on_exception attribute is passed in as a String while the if @m_restart_on_exception statement is expecting a boolean, either TrueClass or FalseClass. The Group calling code parses options into Strings, so modified the if statement to check a string value.

[datwiz]

Didn't mention why - if String is always evaluating to true in the if statement resulting in the actual value of the flag being ignored - .e.g. always retrying