Not possible to authenticate against AD if krb5_ccache_type = FILE

In 'pam_winbind.conf' the following options are set:

krb5_auth = yes 
krb5_ccache_type = FILE 

and in 'smb.conf' kerberos method is set: 

kerberos method = system keytab

An attempt to authenticate against Active Directory (AD) is not possible. 
The error message is similar to:

--
0xb7744038] STATE: ITEM(PAM_AUTHTOK) = 0xb7751460
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): [pamh:
0xb7744038] STATE: ITEM(PAM_CONV) = 0xb77524d8
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): getting password
(0x00001191)
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): pam_get_item
returned a password
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): Verify user
'doudou'
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): CONFIG file:
krb5_ccache_type 'FILE'
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): enabling krb5
login flag
Jul  6 15:29:35 cobu0083 sshd[11420]: pam_winbind(sshd:auth): enabling request
for a FILE krb5 ccache
Jul  6 15:29:36 cobu0083 sshd[11420]: pam_winbind(sshd:auth): request
wbcLogonUser failed: WBC_ERR_AUTH_ERROR, PAM error: PAM_AUTH_ERR (7), NTSTATUS:
NT_STATUS_LOGON_FAILURE, Error message was: Logon failure
Jul  6 15:29:36 cobu0083 sshd[11420]: pam_winbind(sshd:auth): user 'doudou'
denied access (incorrect password or invalid membership)
Jul  6 15:29:36 cobu0083 sshd[11420]: pam_winbind(sshd:auth): [pamh:
--

The value set for kerberos method is probably wrong. It is necessary to choose the right value
depending on the ticket verification being used.

The possible settings for kerberos method are:

secrets only - use only the secrets for ticket verification (default)
system keytab - use only the system keytab for ticket verification
dedicated keytab - use a dedicated keytab for ticket verification.
secrets and keytab - use the secrets.tdb first, then the system keytab

In most of the cases the latter does fit.