Allow additional arguments to be passed into hooks

If a packager wants to be able to support addititional arguments on his
hook this will allow them to setup the configuration with these arguments.

For example this would allow a hook developer to add support for a --debug
flag to change the level of debugging in his hook.

In order to complete this task, I had to vendor in the latest
github.com://opencontainers/runtime-tools, which caused me to have to fix a
Mount and Capability interface calls

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/opencontainers/runtime-tools/filepath/abs.go

@@ -0,0 +1,48 @@
+package filepath
+
+import (
+	"regexp"
+	"strings"
+)
+
+var windowsAbs = regexp.MustCompile(`^[a-zA-Z]:\\.*$`)
+
+// Abs is a version of path/filepath's Abs with an explicit operating
+// system and current working directory.
+func Abs(os, path, cwd string) (_ string, err error) {
+	if IsAbs(os, path) {
+		return Clean(os, path), nil
+	}
+	return Clean(os, Join(os, cwd, path)), nil
+}
+
+// IsAbs is a version of path/filepath's IsAbs with an explicit
+// operating system.
+func IsAbs(os, path string) bool {
+	if os == "windows" {
+		// FIXME: copy hideous logic from Go's
+		// src/path/filepath/path_windows.go into somewhere where we can
+		// put 3-clause BSD licensed code.
+		return windowsAbs.MatchString(path)
+	}
+	sep := Separator(os)
+
+	// POSIX has [1]:
+	//
+	// > If a pathname begins with two successive <slash> characters,
+	// > the first component following the leading <slash> characters
+	// > may be interpreted in an implementation-defined manner,
+	// > although more than two leading <slash> characters shall be
+	// > treated as a single <slash> character.
+	//
+	// And Boost treats // as non-absolute [2], but Linux [3,4], Python
+	// [5] and Go [6] all treat // as absolute.
+	//
+	// [1]: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
+	// [2]: https://github.com/boostorg/filesystem/blob/boost-1.64.0/test/path_test.cpp#L861
+	// [3]: http://man7.org/linux/man-pages/man7/path_resolution.7.html
+	// [4]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/path-lookup.md?h=v4.12#n41
+	// [5]: https://github.com/python/cpython/blob/v3.6.1/Lib/posixpath.py#L64-L66
+	// [6]: https://go.googlesource.com/go/+/go1.8.3/src/path/path.go#199
+	return strings.HasPrefix(path, string(sep))
+}