Set explicit patch target

[ofek]

What does this PR do?

Like

datadog-agent/omnibus/config/software/datadog-agent-integrations-py2.rb

Lines 248 to 253 in ac5bcc6

	# Patch applies to only one file: set it explicitly as a target, no need for -p
	if windows?
	patch :source => "create-regex-at-runtime.patch", :target => "#{python_2_embedded}/Lib/site-packages/yaml/reader.py"
	else
	patch :source => "create-regex-at-runtime.patch", :target => "#{install_dir}/embedded/lib/python2.7/site-packages/yaml/reader.py"
	end

Motivation

          [Builder: pip2] I | 2019-08-19T21:26:36-04:00 | Build pip2: 0.3438s
The following shell command exited with status 3:
    $ bash -c 'patch -p1 -i ../../../../dev/go/src/github.com/DataDog/datadog-agent/omnibus/config/patches/pip2/remove-python27-deprecation-warning.patch'
Output:
    patching file src/pip/_internal/cli/base_command.py
Error:
    Assertion failed: hunk, file ../patch-2.5.9-src/patch.c, line 354

[albertvaka]

LGTM