ZOOKEEPER-2735: fix typos in shell scripts

This PR contains corrections for some spelling typos in shell scripts.

I also create the issue in JIRA [ZOOKEEPER-2735](https://issues.apache.org/jira/browse/ZOOKEEPER-2735)

Author: woojin.joe <woojin.joe@linecorp.com>

Reviewers: Michael Han <hanm@apache.org>

Closes #204 from not-for-me/master

bin/zkCleanup.sh

@@ -25,7 +25,7 @@
 # relative to the canonical path of this script.
 #
 
-# use POSTIX interface, symlink is followed automatically
+# use POSIX interface, symlink is followed automatically
 ZOOBIN="${BASH_SOURCE-$0}"
 ZOOBIN="$(dirname "${ZOOBIN}")"
 ZOOBINDIR="$(cd "${ZOOBIN}"; pwd)"

bin/zkCli.sh

@@ -25,7 +25,7 @@
 # relative to the canonical path of this script.
 #
 
-# use POSTIX interface, symlink is followed automatically
+# use POSIX interface, symlink is followed automatically
 ZOOBIN="${BASH_SOURCE-$0}"
 ZOOBIN="$(dirname "${ZOOBIN}")"
 ZOOBINDIR="$(cd "${ZOOBIN}"; pwd)"

bin/zkServer.sh

@@ -22,7 +22,7 @@
 #
 
 
-# use POSTIX interface, symlink is followed automatically
+# use POSIX interface, symlink is followed automatically
 ZOOBIN="${BASH_SOURCE-$0}"
 ZOOBIN="$(dirname "${ZOOBIN}")"
 ZOOBINDIR="$(cd "${ZOOBIN}"; pwd)"