rollback mysql driver

this https://github.com/go-sql-driver/mysql/pull/302 seems to have pretty much
crippled the ability to use mysql, so we need to lock a version before that
until that issue gets fixed.

vendor/github.com/go-sql-driver/mysql/packets.go

@@ -35,7 +35,7 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
 			}
 			errLog.Print(err)
 			mc.Close()
-			return nil, ErrInvalidConn
+			return nil, driver.ErrBadConn
 		}
 
 		// packet length [24 bit]
@@ -57,7 +57,7 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
 			if prevData == nil {
 				errLog.Print(ErrMalformPkt)
 				mc.Close()
-				return nil, ErrInvalidConn
+				return nil, driver.ErrBadConn
 			}
 
 			return prevData, nil
@@ -71,7 +71,7 @@ func (mc *mysqlConn) readPacket() ([]byte, error) {
 			}
 			errLog.Print(err)
 			mc.Close()
-			return nil, ErrInvalidConn
+			return nil, driver.ErrBadConn
 		}
 
 		// return data if this was the last packet
@@ -137,14 +137,10 @@ func (mc *mysqlConn) writePacket(data []byte) error {
 			if cerr := mc.canceled.Value(); cerr != nil {
 				return cerr
 			}
-			if n == 0 && pktLen == len(data)-4 {
-				// only for the first loop iteration when nothing was written yet
-				return errBadConnNoWrite
-			}
 			mc.cleanup()
 			errLog.Print(err)
 		}
-		return ErrInvalidConn
+		return driver.ErrBadConn
 	}
 }
 
@@ -278,7 +274,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// ClientFlags [32 bit]
@@ -366,7 +362,7 @@ func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add the scrambled password [null terminated string]
@@ -385,7 +381,7 @@ func (mc *mysqlConn) writeClearAuthPacket() error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add the clear password [null terminated string]
@@ -408,7 +404,7 @@ func (mc *mysqlConn) writeNativeAuthPacket(cipher []byte) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add the scramble
@@ -429,7 +425,7 @@ func (mc *mysqlConn) writeCommandPacket(command byte) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add command byte
@@ -448,7 +444,7 @@ func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add command byte
@@ -469,7 +465,7 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// Add command byte
@@ -935,7 +931,7 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 	if data == nil {
 		// can not take the buffer. Something must be wrong with the connection
 		errLog.Print(ErrBusyBuffer)
-		return errBadConnNoWrite
+		return driver.ErrBadConn
 	}
 
 	// command [1 byte]