pgrep: warning about 15+ chars name only if zero matches found

This avoids situations where longer regex which matches short-named proc is used.
Test for pgrep updated.
1 job for pgrep_long_pattern_warn in 1 minute and 58 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #8083511
MakeCheck

00:01:58