+++ This bug was initially created as a clone of Bug #582891 +++

Description of problem:
1. umask should return the current umask when called with no parameter, and should set the umask when it is called with a parameter. It can only return the previous umask but not the current umask. Or There should be a separate cmd to provide this feature(like " mount"/"mounts")

2. the return value should be more human readable.
The return value now is just calculate the oct bit value, which is very confused.
e.g. 
current return value is 18 for mode 022, instead of "022" or "0022"
022->000 010 010->2^1+2^4->18


Version-Release number of selected component (if applicable):
libguestfs-1.0.85-1.fc12.3.x86_64,  latest git version

How reproducible:
100%

Steps to Reproduce:
1.
2.
3.