patches errors from clippy::seek_to_start_instead_of_rewind

https://rust-lang.github.io/rust-clippy/master/index.html#seek_to_start_instead_of_rewind

bucket_map/src/bucket_storage.rs

@@ -317,7 +317,7 @@ impl BucketStorage {
         data.seek(SeekFrom::Start(capacity * cell_size as u64 - 1))
             .unwrap();
         data.write_all(&[0]).unwrap();
-        data.seek(SeekFrom::Start(0)).unwrap();
+        data.rewind().unwrap();
         measure_new_file.stop();
         let mut measure_flush = Measure::start("measure_flush");
         data.flush().unwrap(); // can we skip this?

rbpf-cli/src/main.rs

@@ -22,7 +22,7 @@ use {
     std::{
         fmt::{Debug, Formatter},
         fs::File,
-        io::{Read, Seek, SeekFrom},
+        io::{Read, Seek},
         path::Path,
         time::{Duration, Instant},
     },
@@ -244,7 +244,7 @@ before execting it in the virtual machine.",
     let mut file = File::open(Path::new(program)).unwrap();
     let mut magic = [0u8; 4];
     file.read_exact(&mut magic).unwrap();
-    file.seek(SeekFrom::Start(0)).unwrap();
+    file.rewind().unwrap();
     let mut contents = Vec::new();
     file.read_to_end(&mut contents).unwrap();
     let syscall_registry = register_syscalls(&invoke_context.feature_set, true).unwrap();

runtime/src/append_vec.rs

@@ -333,7 +333,7 @@ impl AppendVec {
         // expensive.
         data.seek(SeekFrom::Start((size - 1) as u64)).unwrap();
         data.write_all(&[0]).unwrap();
-        data.seek(SeekFrom::Start(0)).unwrap();
+        data.rewind().unwrap();
         data.flush().unwrap();
 
         //UNSAFE: Required to create a Mmap

runtime/src/cache_hash_data.rs

@@ -126,7 +126,7 @@ impl CacheHashDataFile {
         // expensive.
         data.seek(SeekFrom::Start(capacity - 1)).unwrap();
         data.write_all(&[0]).unwrap();
-        data.seek(SeekFrom::Start(0)).unwrap();
+        data.rewind().unwrap();
         data.flush().unwrap();
         Ok(unsafe { MmapMut::map_mut(&data).unwrap() })
     }