Fix an issue due to copy-paste problem that made that the Graceful Exit
test to be flaky.
The test uses a time created at the beginning of the test for avoiding
to get undeterministic time differences due to the fact of the response
time variation by the DB queries, however some part of the test were
using a current time rather than this base time, so they have been
addressed.
Change-Id: I4786f06209e041269875c07798a44c2850478438
Add a command to the satellite for cleaning up the Graceful Exit (a.k.a
GE) transfer queue items of nodes that have exited.
The commit adds to the GE satellite DB a couple of new methods, and its
corresponding test, for performing the operations of the new command.
Change-Id: I29a572a59689d63b24990ac13c52e76d65aaa917