blockjob: rename block_job_is_paused()

blockjob: rename block_job_is_paused()

The block_job_is_paused() function name is not great because callers
only use it to determine whether pausing has been requested.  Rename it
to highlight those semantics and remove it from the public header file
as there are no external callers.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1466096189-6477-3-git-send-email-stefanha@redhat.com