TT#12304 Add man-db as dependency to ngcp-nth-{ce,pro}

man-db is no longer "Priority: important" on Debian/stretch,
therefore the man(1) tool is missing on stretch otherwise.

Change-Id: I880f4a545c7d6db1edf71dc123e3de0746f780e2

debian/control

@@ -176,6 +176,7 @@ Depends:
  locales-all,
  lsb-release,
  lsof,
+ man-db,
  mytop,
  ngcp-bulk-processor,
  ngcp-inventory,
@@ -221,6 +222,7 @@ Depends:
  locales-all,
  lsb-release,
  lsof,
+ man-db,
  mytop,
  ngcp-bulk-processor,
  ngcp-klish-config,