vty: make retrieve-imeisv-early configurable

Prepare for Rhizomatica's subscriber on demand use case, in which the
network access is disabled by default for new subscribers, but the IMEI
is required in the HLR to find out which user has which IMSI. Due to the
network access being disabled, the location update request towards the
HLR fails and the MS gets rejected, so we need to get the IMEI early.

Related: OS#2542, OS#3755
Change-Id: I256224194c3b8caf2b58a88d11dccd32c569201f
2 files changed