cantrip-os-rootserver: quiet cargo complaint

Rename "main.rs" to "lib.rs" to quiet an innocuous cargo complaint.

Change-Id: I6ab99c1417d73d077d147e8d4695d3253e1742f3

cantrip-os-rootserver/Cargo.toml

diff --git a/cantrip-os-rootserver/Cargo.toml b/cantrip-os-rootserver/Cargo.toml
index 7175113..35ab864 100644
--- a/cantrip-os-rootserver/Cargo.toml
+++ b/cantrip-os-rootserver/Cargo.toml
@@ -38,7 +38,7 @@
 
 [lib]
 name = "cantrip_os_rootserver"
-path = "src/main.rs"
+path = "src/lib.rs"
 crate-type = ["staticlib"]
 
 [dependencies.cantrip-os-common]

cantrip-os-rootserver/src/lib.rs

diff --git a/cantrip-os-rootserver/src/main.rs b/cantrip-os-rootserver/src/lib.rs
similarity index 100%
rename from cantrip-os-rootserver/src/main.rs
rename to cantrip-os-rootserver/src/lib.rs