Calling makeModuleSetUpAndTestCaseClass results already with preparing some
environment and also test classes will run the promises, so they would never
execute test_kvm_sanity_check.

So create a method sanityCheck to check the environment and depending of the
result call or not makeModuleSetUpAndTestCaseClass and skipIf test cases
when environment is not sane enough.

Also drop now needless etc/promise directory.

As possible cover promises in tests.

Assert that machine running tests is good enough for KVM tests.

monitor-boostrap.pid existence is unpredictible.

In test nodes we put the software_root folder out of the webrunner so we
can keep it for the following tests. Except that the shared folder has
been introduced by default recently, and it is still inside the webrunner.

Thus, between 2 tests the webrunner is deleted, so the shared parts are too,
but not the SR folder (which is marked as completed). Then in the successive tests
the software release fails to build, or the insances fail to isntanciate.

/reviewed-on nexedi/slapos!654