build: fixes for compiling with -Werror=format-security

Nightly builds on Fedora Rawhide (x86_64 and i686) started to fail with the
following error:

  cli-rpc-ops.c: In function 'gf_cli_get_vol_opt_cbk':
  cli-rpc-ops.c:9339:25: error: format not a string literal and no format arguments [-Werror=format-security]
                           cli_err (msg);
                           ^

The cli_err() should be called with a format-string like "%s" to prevent
unexpected errors.

Change-Id: I6a287795fb8b7a305c8f14323456eeabf68d100c
BUG: 1134773
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/8560
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>