Use retval from insert() rather than testing with contains()
Use retval from insert() rather than testing with contains()

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>

trgill/stratisd,mulkieran/stratisd,stratis-storage/stratisd,mulkieran/stratisd,stratis-storage/stratisd,trgill/stratisd,stratis-storage/stratisd