LU-17015 gss: bump token buffer size to 16KiB

LU-17015 gss: bump token buffer size to 16KiB

A 4 KiB large buffer is not enough to hold the GSS token under some
circumstances. So bump GSS_CTX_INIT_MAX_LEN value to 16 KiB.

Lustre-change: https://review.whamcloud.com/52475
Lustre-commit: TBD (from 43a540207da0198cc9c45b3c6312c555702b56cb)

Fixes: 9758129177 ("LU-17015 gss: support large kerberos token on client")
Test-Parameters: trivial kerberos=true testlist=sanity-krb5
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I8e72f1447593d2bf2ae537fcc920ceee20e93c09
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52628
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>