[test suite] added --cmd-verbose to control fwknop command verbosity levels

This commit provides an easy way to control how verbose fwknop command
execution will be.  For example, fwknopd only calls hex_dump() against
SPA packets when --verbose > 2, so invoking the tests suite as follows
will result in hex_dump() being included in fwknopd output (see the
output/1_fwknopd.test file:

./test-fwknop.pl --include "Rijndael.*complete.*22" --test-limit 1 --cmd-verbose "--verbose --verbose --verbose"

[+] candidate SPA packet payload:

  0x0000:  39 62 72 51 58 75 7a 4b  57 54 53 67 57 56 35 66 9brQXuzKWTSgWV5f
  0x0010:  73 63 78 42 35 78 69 51  65 6c 55 4f 53 78 69 45 scxB5xiQelUOSxiE
  0x0020:  51 30 59 6a 41 50 70 31  4f 70 43 62 32 51 4a 4c Q0YjAPp1OpCb2QJL
  0x0030:  48 34 42 65 68 64 6d 47  35 49 31 50 36 2f 5a 69 H4BehdmG5I1P6/Zi
  0x0040:  6a 34 4b 41 62 34 53 68  6a 59 66 4f 71 2b 46 6c j4KAb4ShjYfOq+Fl
  0x0050:  4a 35 52 75 70 33 39 6f  6e 65 42 79 72 51 46 57 J5Rup39oneByrQFW
  0x0060:  61 38 6c 37 63 48 6e 38  5a 54 36 59 6e 55 56 47 a8l7cHn8ZT6YnUVG
  0x0070:  50 36 6e 53 6f 69 30 61  70 72 32 52 39 62 6b 56 P6nSoi0apr2R9bkV
  0x0080:  37 50 61 67 41 61 6b 49  44 63 58 59 44 6b 2f 64 7PagAakIDcXYDk/d
  0x0090:  67 51 45 61 37 39 32 6f  30 4d 38 6e 30 30 6e 35 gQEa792o0M8n00n5
  0x00a0:  55                                               U