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/clean.go

@@ -0,0 +1,74 @@
+package filepath
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Clean is an explicit-OS version of path/filepath's Clean.
+func Clean(os, path string) string {
+	abs := IsAbs(os, path)
+	sep := Separator(os)
+	elements := strings.Split(path, string(sep))
+
+	// Replace multiple Separator elements with a single one.
+	for i := 0; i < len(elements); i++ {
+		if len(elements[i]) == 0 {
+			elements = append(elements[:i], elements[i+1:]...)
+			i--
+		}
+	}
+
+	// Eliminate each . path name element (the current directory).
+	for i := 0; i < len(elements); i++ {
+		if elements[i] == "." && len(elements) > 1 {
+			elements = append(elements[:i], elements[i+1:]...)
+			i--
+		}
+	}
+
+	// Eliminate each inner .. path name element (the parent directory)
+	// along with the non-.. element that precedes it.
+	for i := 1; i < len(elements); i++ {
+		if i == 1 && abs && sep == '\\' {
+			continue
+		}
+		if i > 0 && elements[i] == ".." {
+			elements = append(elements[:i-1], elements[i+1:]...)
+			i -= 2
+		}
+	}
+
+	// Eliminate .. elements that begin a rooted path:
+	// that is, replace "/.." by "/" at the beginning of a path,
+	// assuming Separator is '/'.
+	offset := 0
+	if sep == '\\' {
+		offset = 1
+	}
+	if abs {
+		for len(elements) > offset && elements[offset] == ".." {
+			elements = append(elements[:offset], elements[offset+1:]...)
+		}
+	}
+
+	cleaned := strings.Join(elements, string(sep))
+	if abs {
+		if sep == '/' {
+			cleaned = fmt.Sprintf("%c%s", sep, cleaned)
+		} else if len(elements) == 1 {
+			cleaned = fmt.Sprintf("%s%c", cleaned, sep)
+		}
+	}
+
+	// If the result of this process is an empty string, Clean returns
+	// the string ".".
+	if len(cleaned) == 0 {
+		cleaned = "."
+	}
+
+	if cleaned == path {
+		return path
+	}
+	return Clean(os, cleaned)
+}