travis: Perform MinGW builds on Fedora 30
travis: Perform MinGW builds on Fedora 30

Since libvirt-jenkins-ci commit 3c5ac0af41ba, MinGW packages
are installed on Fedora 30 rather than Fedora Rawhide, so we
need to update the Travis CI configuration accordingly.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Fabiano Fidêncio <2931bae082ef9bc04523ba759c03a4778316d48f@redhat.com>

crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,libvirt/libvirt,libvirt/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,crobinso/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,olafhering/libvirt,andreabolognani/libvirt,crobinso/libvirt,andreabolognani/libvirt,zippy2/libvirt,andreabolognani/libvirt,olafhering/libvirt,jfehlig/libvirt,jardasgit/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,crobinso/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,zippy2/libvirt,libvirt/libvirt