input_seqsrc: Increase required verbosity level for noisy printf's

The "freeing old source", "initialized new seqsrc", and "resetting
source" debugging printf's generated by the seqsrc tracking code are
low-level, and noisy. They should require a higher verbosity level than
the debug message printed when a dropped container is detected.

Increase the required verbosity level for these messages from 5 to 6.