CA-83040: Simplify check_sr_exists_for_host
CA-83040: Simplify check_sr_exists_for_host

check_sr_exists_for_host had some nested-if spaghetti logic that was
unessessary. We simplify it by just calling host_has_pbd_for_sr directly, since
that function returns false if the SR isn't valid.

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

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