A related patch has been committed upstream: https://github.com/beekhof/pacemaker/commit/cd71bcc

Note the two additional actions (with suggested timeouts):

    <action name="stop" timeout="20s"/>
    <action name="start" timeout="20s"/>


# fencing/stonith_admin -M -a fence_xvm
<resource-agent name="fence_xvm" shortdesc="Fence agent for virtual machines">
  <longdesc>fence_xvm is an I/O Fencing agent which can be used withvirtual machines.</longdesc>
  <parameters>
    <parameter name="debug">
      <getopt mixed="-d"/>
      <content type="boolean"/>
      <shortdesc lang="en">Specify (stdin) or increment (command line) debug level</shortdesc>
    </parameter>
    <parameter name="ip_family">
      <getopt mixed="-i"/>
      <content type="string" default="auto"/>
      <shortdesc lang="en">IP Family ([auto], ipv4, ipv6)</shortdesc>
    </parameter>
    <parameter name="multicast_address">
      <getopt mixed="-a"/>
      <content type="string"/>
      <shortdesc lang="en">Multicast address (default=225.0.0.12 / ff05::3:1)</shortdesc>
    </parameter>
    <parameter name="ipport">
      <getopt mixed="-p"/>
      <content type="string" default="1229"/>
      <shortdesc lang="en">Multicast or VMChannel IP port (default=1229)</shortdesc>
    </parameter>
    <parameter name="retrans">
      <getopt mixed="-r"/>
      <content type="string" default="20"/>
      <shortdesc lang="en">Multicast retransmit time (in 1/10sec; default=20)</shortdesc>
    </parameter>
    <parameter name="auth">
      <getopt mixed="-C"/>
      <content type="string" default="sha256"/>
      <shortdesc lang="en">Authentication (none, sha1, [sha256], sha512)</shortdesc>
    </parameter>
    <parameter name="hash">
      <getopt mixed="-c"/>
      <content type="string" default="sha256"/>
      <shortdesc lang="en">Packet hash strength (none, sha1, [sha256], sha512)</shortdesc>
    </parameter>
    <parameter name="key_file">
      <getopt mixed="-k"/>
      <content type="string" default="/etc/cluster/fence_xvm.key"/>
      <shortdesc lang="en">Shared key file (default=/etc/cluster/fence_xvm.key)</shortdesc>
    </parameter>
    <parameter name="port" required="0">
      <getopt mixed="-H"/>
      <content type="string"/>
      <shortdesc lang="en">Virtual Machine (domain name) to fence</shortdesc>
    </parameter>
    <parameter name="use_uuid">
      <getopt mixed="-u"/>
      <content type="string" default="0"/>
      <shortdesc lang="en">Treat [domain] as UUID instead of domain name. This is provided for compatibility with older fence_xvmd installations.</shortdesc>
    </parameter>
    <parameter name="action">
      <getopt mixed="-o"/>
      <content type="string" default="reboot"/>
      <shortdesc lang="en">Fencing action (null, off, on, [reboot], status, list, monitor, metadata)</shortdesc>
    </parameter>
    <parameter name="timeout">
      <getopt mixed="-t"/>
      <content type="string" default="30"/>
      <shortdesc lang="en">Fencing timeout (in seconds; default=30)</shortdesc>
    </parameter>
    <parameter name="domain">
      <!-- DEPRECATED; FOR COMPATIBILITY ONLY -->
      <content type="string"/>
      <shortdesc lang="en">Virtual Machine (domain name) to fence (deprecated; use port)</shortdesc>
    </parameter>
  </parameters>
  <actions>
    <action name="null"/>
    <action name="on"/>
    <action name="off"/>
    <action name="reboot"/>
    <action name="metadata"/>
    <action name="status"/>
    <action name="monitor"/>
    <action name="list"/>
    <action name="stop" timeout="20s"/>
    <action name="start" timeout="20s"/>
  </actions>
</resource-agent>

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Cause: Overzealous validation by the cluster shell.
Consequence: The shell complained when updating configurations that included fencing devices.
Fix: Massage the retrieved fencing agent metadata to advertise 'start' and 'stop' as supported actions (as these actions are handled by the stonith daemon).

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2012-0846.html