profiles: prpl: disable sysntpd service

time-manager's managed chrony should be the sole system component
responsible for time management. Currently, Busybox's `ntpd` is also
running, attempting to perform the same task, which may cause
undesirable system behavior.

This issue became more apparent after commit 568acaccf8b4 ("ci:
cdrouter: fix unable-to-start-connection-to-usp-agent by enabling NTP
sync"), where both Chrony and ntpd began using the same NTP pools,
0.europe.pool.ntp.org and 1.europe.pool.ntp.org.

To address this, we should make `time-manager` exclusively responsible
for system time management, remove Busybox's `ntpd`, add a CI check to
prevent this regression in the future.

References: PCF-1257, PCF-1104
Suggested-by: Vincent Harle <vincent.harle@softathome.com>
Signed-off-by: Petr Štetiar <petr.stetiar@prplfoundation.org>
(cherry picked from commit 8e1f17f34b3c9a0b174a7b22df0be889390a637b)

.gitlab/tests/cram/generic/busybox.t

@@ -0,0 +1,8 @@
+Create R alias:
+
+  $ alias R="${CRAM_REMOTE_COMMAND:-}"
+
+Assure that sysntpd is not running:
+
+  $ R "pgrep -ax ntpd"
+  [1]

profiles/prpl.yml

@@ -246,4 +246,6 @@ diffconfig: |
           # CONFIG_PACKAGE_libustream-wolfssl is not set
           CONFIG_PACKAGE_libustream-openssl=y
           CONFIG_LIGHTTPD_CRYPTOLIB_NETTLE=y
+          CONFIG_BUSYBOX_CUSTOM=y
           CONFIG_BUSYBOX_CONFIG_FLOAT_DURATION=y
+          # CONFIG_BUSYBOX_CONFIG_NTPD is not set