Use retry strategy properly for synchronization with server

[jingtang10]

where is this used?

Originally posted by @yigit in https://github.com/google/android-fhir/pull/482#discussion_r639405734

[deepankarb]

@epicadk is working on this.

[omarismail94]

Closing as we do this now as part of the network configuration data class in FHIR Engine