lttng: Only install rbd-replay-prep when enabled

Signed-off-by: Adam Crume <adamcrume@gmail.com>
lttng: Suppress errors from broken lttng-gen-tp when configuring

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>