lttng: Test for sane lttng-gen-tp

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Check that the main babeltrace header is present

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Check for babeltrace when autoconfiguring lttng

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Only install rbd-replay-prep when enabled

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Add informational messages to configure.ac

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Remove tracing-specfic local variables when lttng disabled

Signed-off-by: Adam Crume <adamcrume@gmail.com>