Move all opens in auth_token to be in context
Move all opens in auth_token to be in context

This commit switches the use of open() to be in a with context. This
will prevent leaking file descriptors because using a context
provides an inherent close(). Prior to this commit it was possible
that an exception or error during the write() call could prevent
close() from running.

Change-Id: Ib13fe651d41f0eafea23a1c96c6c64d405de7e49

sdpp/python-keystoneclient,magic0704/python-keystoneclient,jamielennox/python-keystoneclient,citrix-openstack-build/python-keystoneclient,ging/python-keystoneclient,alexpilotti/python-keystoneclient,metacloud/python-keystoneclient,ntt-sic/python-keystoneclient,alexpilotti/python-keystoneclient,citrix-openstack-build/python-keystoneclient,darren-wang/ksc,ntt-sic/python-keystoneclient,ntt-sic/python-keystoneclient,sdpp/python-keystoneclient,metacloud/python-keystoneclient,darren-wang/ksc,Mercador/python-keystoneclient,citrix-openstack-build/python-keystoneclient,jamielennox/python-keystoneclient,Mercador/python-keystoneclient,magic0704/python-keystoneclient,jamielennox/python-keystoneclient,klmitch/python-keystoneclient,klmitch/python-keystoneclient,ging/python-keystoneclient