build: Add a comment about workaround for RPM 4.8 in CentOS 6.4

Signed-off-by: Euan Harris <euan.harris@citrix.com>
build: Fix mock's RPM repository path

Mock still assumes that RPMS can be found in $HOME/rpmbuild/RPMS.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #111 from euanh/build-improvements

build: Fix mock's RPM repository path