Summary:
We check if $HOME/.pki and $HOME/.pki/nssdb exist; if they do, then we use
this path. Otherwise, use ${XDG_DATA_HOME:-$HOME/.local/share}/pki/nssdb

Test Plan:
Create dummy empty dir and set HOME to it. Then, check if getUserDb returns:
1. $HOME/.pki/nssdb when this path exists;
2. $HOME/.local/share/pki/nssdb when $HOME/.pki/nssdb does not and XDG_DATA_HOME is not defined;
3. $XDG_DATA_HOME/pki/nssdb when $HOME/.pki/nssdb does not exist and XDG_DATA_HOME is defined.

Reviewers: mt

Reviewed By: mt

Bug #: 818686

Differential Revision: https://phabricator.services.mozilla.com/D14007

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extra : source : 45f82855824be40a6a2b74632dda5e9e6f89a5d0