Close the provider DB file when done with it.

The mobile_provider_open_db function opens the provider DB file,
reads the whole thing in, and parses it. It should have then been
closing the file, but wasn't. Now it does.

BUG=none
TEST=unit tests still run

Change-Id: I2623be7a4a0df913ffe39dac9259d6f13aaaea12
diff --git a/src/mobile_provider.c b/src/mobile_provider.c
index 6d60538..59c2d56 100644
--- a/src/mobile_provider.c
+++ b/src/mobile_provider.c
@@ -406,6 +406,7 @@
         g_strfreev(fields);
         g_free(state);
         errno = ENOSYS;
+        fclose(dbfile);
         return NULL;
       }
       firstline = 0;
@@ -425,6 +426,7 @@
     }
     g_strfreev(fields);
   }
+  fclose(dbfile);
   if (state->country == NULL && state->provider == NULL) {
     g_hash_table_destroy(state->name_table);
     g_hash_table_destroy(state->network_table);