TT#36817 Conflict with chrony in ngcp-services-*

Noticed when running against recent versions of
Debian/stretch AMI on EC2 (e.g. ami-8a745cf3), failing with:

| The following packages have unmet dependencies:
|
|  ngcp-services-ce : Depends: ntp but it is not going to be installed

Caused by:

| # sudo apt-get install ntp
| [...]
| The following packages will be REMOVED:
|   chrony
| The following NEW packages will be installed:
|   libopts25 ntp

Change-Id: I6216fe81f758eb536fe8a5e981c95a5f8f8ea7fe

debian/control

@@ -330,6 +330,7 @@ Depends:
 Provides:
  ngcp-services,
 Conflicts:
+ chrony,
  ngcp-services,
  initscripts,
  insserv,
@@ -403,6 +404,7 @@ Depends:
 Provides:
  ngcp-services,
 Conflicts:
+ chrony,
  ngcp-services,
  initscripts,
  insserv,
@@ -501,6 +503,7 @@ Depends:
 Provides:
  ngcp-services,
 Conflicts:
+ chrony,
  ngcp-services,
  initscripts,
  insserv,