Teach cros_list_buildbot_crashes.py to work inside the chroot.
Teach cros_list_buildbot_crashes.py to work inside the chroot.

Right now, if you run this script from inside the chroot, it assumes
that the googlestorage_account.boto file is stored inside ~/.local.
This is because the constants file is pulled from ~/.local/lib, so
the SOURCE_ROOT value is wrong. Fix constants.py so that the SOURCE_ROOT
directory will be right.

BUG=chromium-os:24908
TEST=Run this script inside the chroot.

Change-Id: Icd6a88f675280e7295e6c46054c13c5862c85eac
Reviewed-on: https://gerrit.chromium.org/gerrit/14939
Commit-Ready: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

zhang0137/chromite,zhang0137/chromite,coreos/chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,coreos/chromite,chadversary/chromiumos.chromite,chadversary/chromiumos.chromite