The Makefile shouldn't call 'configure'

The build 'standard' is that the caller should run
  ./configure
  make

Signed-off-by: David Scott <dave.scott@citrix.com>
configure: add '--disable-tests' option

Unfortunately the unit tests don't work when run as unpriviledged
users inside unprepared chroots. This allows them to be skipped.

By default "./configure && make" will run the unit tests as before.

Signed-off-by: David Scott <dave.scott@citrix.com>
xapi.spec: run "configure"

Signed-off-by: David Scott <dave.scott@citrix.com>
xenserver build: run configure from mk/Makefile

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #1721 from djs55/experiment

Increase mock-friendliness