CA-52663/SCTX-581: default ignoreblank option of vncsnapshot multiply snapshot processes and can lead to OOM in dom
CA-52663/SCTX-581: default ignoreblank option of vncsnapshot multiply
snapshot processes and can lead to OOM in dom

Added --allowblank option to vncsnaphot command. Now vncsnapshot will
return all-blank images immediately, instead of blocking until the
guest wakes up (which could be indefinite).

Signed-off-by: Mike McClurg <d5d39725aee3103039228164deec3c7acc6f60e3@citrix.com>

djs55/xcp-networkd,koushikcgit/xcp-rrdd,johnelse/xcp-rrdd,johnelse/xcp-rrdd,djs55/xcp-networkd,sharady/xcp-networkd,djs55/squeezed,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,koushikcgit/xcp-rrdd,sharady/xcp-networkd,simonjbeaumont/xcp-rrdd,koushikcgit/xcp-networkd,djs55/xcp-rrdd,koushikcgit/xcp-networkd,robhoes/squeezed,simonjbeaumont/xcp-rrdd