env_posix: remove unused page_size_ member
env_posix: remove unused page_size_ member

Change-Id: I4d0d9e6470fc618ec60f325c25852f086f919336
Reviewed-on: http://gerrit.cloudera.org:8080/1982
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>
Tested-by: Todd Lipcon <2c763d726a8c2f6afda9be7e0e56a2caa6bb5e6b@apache.org>

andrwng/kudu,andrwng/kudu,cloudera/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,InspurUSA/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,helifu/kudu,helifu/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,andrwng/kudu,andrwng/kudu,cloudera/kudu,andrwng/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,helifu/kudu,helifu/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,cloudera/kudu,EvilMcJerkface/kudu,cloudera/kudu,andrwng/kudu,andrwng/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,cloudera/kudu,InspurUSA/kudu,cloudera/kudu