test/bdev: limit memory size to 1GB

This helps prepare using the bdev test tools (bdevio and
bdevperf) with a virtio/vhost-scsi initiator.  For virtio
initiators running in the host OS, SPDK must open file
descriptors for every hugepage to pass to the vhost
target.  vhost typically limits the number of memory
regions to 8 - meaning 2MB hugepages generally will not
work, but even for 1GB hugepages we need to limit it so
that we do not default to trying to use all of the
hugepages.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: If1e6e91cea096421b8dc5e707435e287ca14bb6e

Reviewed-on: https://review.gerrithub.io/374013
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>

test/lib/bdev/common.c

@@ -46,4 +46,5 @@ bdevtest_init(const char *config_file, const char *cpumask,
 	opts->name = "bdevtest";
 	opts->config_file = config_file;
 	opts->reactor_mask = cpumask;
+	opts->mem_size = 1024;
 }