Use spnego dedicated keytab

Kerberos is one of the authentication methods that impala provides.
Kerberized impala uses its keytab that has impala principal for authentication.

kerberos authentication can be applied by setting '-principal' and '-keytab_file' flags.
Further more, It is possible to kerberize impala web console by having --webserver_require_spnego as true.

The problem is impala uses just one keytab file. Therefore, a keytab must have both impala and HTTP spnego principal If you want to kerberize web console too.

As far as i know, Other service like hadoop, hive and etc provides a option to use http spnego dedicated keytab file and there are cases that using seperate http spnego keytab and service keytab. So providing a way to use another keytab file for http spnego will make users handle kerberos keytab file more easily.