Construct EnterpriseSpecificIdCalculator only once after the boot phase

is completed.

Construct the EnterpriseSpecificIdCalculator object after boot phase is
complete, as some of the dependencies(telephony and wifi service) for
this class are not properly initialized before that.

Bug: 191741106
Test: atest com.android.cts.devicepolicy.MixedDeviceOwnerTest#testEnrollmentSpecificIdCorrectCalculation com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testEnrollmentSpecificIdCorrectCalculation com.android.cts.devicepolicy.MixedDeviceOwnerTest#testEnrollmentSpecificIdEmptyAndMultipleSet com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testEnrollmentSpecificIdEmptyAndMultipleSet

Change-Id: I20927cdc6844591f12d390ced7f1471733602a81