packaging: spec: add mailcap dependency

Used explicitly at ServletUtils.java

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1073548
Reported By: Alexander Wels <awels@redhat.com>
Change-Id: Ib2f518bd25675ecc1d683e18a34d9a444eda4b6b
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>