fs_mgr: Suppress SkipMountingPartitions log in ReadFstabFromFile

Minor refactoring and renaming, goal is to make the follow-up patch
easier to read.

Bug: 184132970
Test: Presubmit
Change-Id: I66416161b30ac310934d901cbaf11bc926e2cbf7
diff --git a/init/selinux.cpp b/init/selinux.cpp
index 62c4586..2d3e06e 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -658,7 +658,7 @@
         extra_fstab.emplace_back(std::move(entry));
     }
 
-    SkipMountingPartitions(&extra_fstab);
+    SkipMountingPartitions(&extra_fstab, true /* verbose */);
     if (extra_fstab.empty()) {
         return;
     }