qa/stanalone: pass options using --<option-name>=<value>

qa/stanalone: pass options using --<option-name>=<value>

not "--<option-name> <value>', otherwise `ceph-authtool` would error
out:

$ CEPH_ARGS='--osd-map-max-advance 1000' bin/ceph-authtool --gen-print-key
bin/ceph-authtool: unexpected '1000'
usage: ceph-authtool keyringfile [OPTIONS]...
....

but using the syntax of `--<option-name>=<value>', it works:

$ CEPH_ARGS='--osd-map-max-advance=1000' bin/ceph-authtool --gen-print-key
AQBAhTNamf5+ABAASkAp/6IGq7LkUTEOMp/fgw==

Signed-off-by: Kefu Chai <kchai@redhat.com>