kudu-tool-test: find path to false at runtime
kudu-tool-test: find path to false at runtime

On macos the false binary is in /usr/bin/false.

Change-Id: I2e2cd346b48c61cfe27fc77ee3cabb681be94ab2
Reviewed-on: http://gerrit.cloudera.org:8080/7959
Reviewed-by: Todd Lipcon <2c763d726a8c2f6afda9be7e0e56a2caa6bb5e6b@apache.org>
Tested-by: Kudu Jenkins

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