Description of problem:
Support backup-volfile-servers with /usr/sbin/glusterfs command .

Version-Release number of selected component (if applicable):
3.5.1

How reproducible:
 /usr/sbin/glusterfs --usage
Usage: glusterfs [-N?V] [-f VOLFILE] [-l LOGFILE] [-L LOGLEVEL] [-s SERVER]
            [-p PIDFILE] [-S SOCKFILE] [--volfile=VOLFILE] [--log-file=LOGFILE]
            [--log-level=LOGLEVEL] [--volfile-server=SERVER] [--acl]
            [--aux-gfid-mount] [--debug] [--enable-ino32[=BOOL]]
            [--fopen-keep-cache[=BOOL]] [--mac-compat[=BOOL]] [--no-daemon]
            [--pid-file=PIDFILE] [--read-only] [--selinux]
            [--socket-file=SOCKFILE] [--volfile-id=KEY]
            [--volfile-server-port=PORT]
            [--volfile-server-transport=TRANSPORT] [--volume-name=XLATOR-NAME]
            [--worm] [--xlator-option=XLATOR-NAME.OPTION=VALUE]
            [--attribute-timeout=SECONDS] [--background-qlen=N]
            [--congestion-threshold=N] [--direct-io-mode[=BOOL]]
            [--dump-fuse=PATH] [--entry-timeout=SECONDS]
            [--gid-timeout=SECONDS] [--negative-timeout=SECONDS]
            [--use-readdirp[=BOOL]] [--volfile-check] [--help] [--usage]
            [--version] --volfile-server=SERVER [MOUNT-POINT]
  or:  glusterfs [OPTION...] --volfile=VOLFILE [MOUNT-POINT]

Steps to Reproduce:
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Actual results:


Expected results:


Additional info: