obtain account details from the active user

BUG=b:20895978

Change-Id: I09336a666e5c84af4a1c8f20509654d878df6e41
diff --git a/usr/lib/portage/pym/portage/const_autotool.py b/usr/lib/portage/pym/portage/const_autotool.py
index 6189d0c..c1dc9d5 100644
--- a/usr/lib/portage/pym/portage/const_autotool.py
+++ b/usr/lib/portage/pym/portage/const_autotool.py
@@ -7,17 +7,19 @@
 		"portageuser", "portagegroup", "rootuser", "rootuid", "rootgid",
 		"PORTAGE_BASH", "PORTAGE_MV"]
 
+import getpass
+import grp
 import os
 
 EPREFIX      = os.path.realpath(os.path.abspath(__file__) + '../' * 7)
 SYSCONFDIR   = os.path.join(EPREFIX, 'etc')
 PORTAGE_BASE = os.path.join(EPREFIX, 'usr/lib/portage')
 
-portagegroup = "eng"
-portageuser  = "vapier"
-rootuser     = "vapier"
-rootuid      = 145691
-rootgid      = 5000
+portagegroup = grp.getgrgid(os.getgid()).gr_name
+portageuser  = getpass.getuser()
+rootuser     = portageuser
+rootuid      = os.getuid()
+rootgid      = os.getgid()
 
 PORTAGE_BASH = "/bin/bash"
 PORTAGE_MV   = "/bin/mv"