Change jxmpp version to 0.4.1-alpha2-SNAPSHOT

Mostly because of 738276e1aca093da16ea160462bdda7523a26a14 in jxmpp,
which fixes fractional seconds parsing.

Which made also the slight change in DelayInformationTest necessary.
VCardProvider should use a safe parser

Where e.g. entity reference expansion is disbled. Note that this affects
only the VCard provider, as it's the only provider in Smack that uses
SAX's DocumentBuilder.

Fixes SMACK-620