restore: clear httpd ccache after restore
so that httpd ccache won't contain old credentials which would make ipa CLI fail with error:
Insufficient access: SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (Decrypt integrity check failed)
https://fedorahosted.org/freeipa/ticket/4726
Reviewed-By: Petr Viktorin <pviktori@redhat.com>