Description of problem:
fencing_snmp.py returns KeyError: '--a'
and the fencing will fail

Version-Release number of selected component (if applicable):
4.0.2

How reproducible:
Always in combination of fence_intelmodular

Steps to Reproduce:
1. /usr/sbin/fence_intelmodular --action=status --ip=XXX.XXX.XXX.XXX --username=snmpv3user --password=XXXXXXXXXX --snmp-version=3 --snmp-auth-prot=SHA --verbose --plug=3 --snmp-sec-level=auth


Actual results:
Traceback (most recent call last):
  File "/usr/sbin/fence_intelmodular", line 92, in <module>
    main()
  File "/usr/sbin/fence_intelmodular", line 87, in main
    result = fence_action(FencingSnmp(options), options, set_power_status, get_power_status, get_outlets_status)
  File "/usr/share/fence/fencing.py", line 810, in fence_action
    status = get_multi_power_fn(tn, options, get_power_fn)
  File "/usr/share/fence/fencing.py", line 743, in get_multi_power_fn
    plug_status = get_power_fn(tn, options)
  File "/usr/sbin/fence_intelmodular", line 41, in get_power_status
    (oid, status) = conn.get("%s.%s"% (STATUSES_OID, options["--plug"]))
  File "/usr/share/fence/fencing_snmp.py", line 106, in get
    cmd = "%s '%s'"% (self.prepare_cmd("snmpget"), self.quote_for_run(oid))
  File "/usr/share/fence/fencing_snmp.py", line 73, in prepare_cmd
    cmd += " -%s '%s'"% (item[1], self.quote_for_run(self.options["--" + item[1]]))
KeyError: '--a'

Expected results:
/usr/bin/snmpget -m '' -Oeqn  -v '3' -a 'SHA' -l 'auth' -A '87654321' -u 'snmpv3user' '85.17.234.138:161' '.1.3.6.1.4.1.343.2.19.1.2.10.202.1.1.6.3'
.1.3.6.1.4.1.343.2.19.1.2.10.202.1.1.6.3 2

Status: ON


Additional info:
I have found the bug, but can't know if it will affect other snmp fencing. But the correction is logic trough my eyes

in the file fencing_snmp.py on line 73 it states:
cmd += " -%s '%s'"% (item[1], self.quote_for_run(self.options["--" + item[1]]))

And it need to be:
cmd += " -%s '%s'"% (item[1], self.quote_for_run(self.options["--" + item[0]]))
I have attached the corrected file