Changes file_path to self.file_path

Changes file_path to self.file_path in ceilometer_config provider
in order to allow purging as specified in ini_file puppet module
readme.

Change-Id: I41f7c83e3a63b9af9e683933aa09bd45d5b18deb
Closes-Bug: 1280329
Fix ensure_packages error

The ceilometer::collector class calls ensure_packages()
on a single package name, but the package name is provided
as a string rather than a one-element array.  This causes an
error of the form:

Error: ensure_packages(): Requires array given (String) at
/usr/share/puppet/modules/ceilometer/manifests/collector.pp:16

This patch corrects the error by passing an array instead
of a string.

Change-Id: I96cedf7561af29d92924746881c52bdd1502365f
Closes-Bug: #1292775
Merge "Changes file_path to self.file_path"
Merge "Fix ensure_packages error"