Fix HTTPKerberosAuth not to treat non-file as a file
Fix HTTPKerberosAuth not to treat non-file as a file

Ensure pos is set to None when the body is not a file
so that HTTPKerberosAuth detects the type of the body correctly.

rbcarson/requests-kerberos,requests/requests-kerberos,AbsoluteMSTR/requests-kerberos,danc86/requests-kerberos,requests/requests-kerberos